Make various lm_info implementations inherit from a base class

The lm_info structure is used to store target specific information about
mapped libraries.  It is currently defined as an opaque type in solist.h
and a pointer to it is included in solist, the target-agnostic object
representing a loaded shared library.  Multiple targets define their own
implementation of lm_info.

In anticipation of using C++ stuff (e.g. vector) in the lm_info objects,
we first need to avoid different definitions of classes with the same
name (which violates the one definition rule).  This patch does it by
having a base class (lm_info_base) from which all the specific lm_info
derive.  Each implementation is renamed to something that makes sense
(e.g. lm_info_aix for AIX).  The next logical step would probably be to
derive directly from so_list, it's not really obvious, so I'll keep that
for another day.

One special case is the Neutrino (nto) support.  It uses SVR4-style
libraries, but overrides some methods.  To do that, it needed to have
its own copy of SVR4's lm_info structure in nto-tdep.c, because it was
just not possible to put it in solib-svr4.h and include that file.  Over
time, that copy got out of sync, which is still the case today.  I can
only assume that the lm_addr function in nto-tdep.c is broken right now.
The first field of the old lm_info was a pointer (gdb_byte *), whereas
in the new lm_info it's an address in the inferior (CORE_ADDR).  Trying
to use that field today probably results in a crash.  With this
refactor, it's now possible to put lm_info_svr4 in solib-svr4.h and just
include it.  I have adapted the code in nto-tdep.c to that it builds,
but it's probably not correct.  Since I don't have the knowledge nor
setup to try this on Neutrino, somebody else would have to fix it.  But
I am confident that I am not making things worse than they already are.

gdb/ChangeLog:

	* solist.h (struct lm_info): Remove.
	(struct lm_info_base): New class.
	(struct so_list) <lm_info>: Change type to lm_info_base *.
	* nto-tdep.c (struct lm_info): Remove.
	(lm_addr): Adjust.
	* solib-aix.c (struct lm_info): Rename to ...
	(struct lm_info_aix): ... this.  Extend lm_info_base.
	(lm_info_p): Rename to ...
	(lm_info_aix_p): ... this, and adjust.
	(solib_aix_new_lm_info, solib_aix_xfree_lm_info,
	solib_aix_parse_libraries, library_list_start_library,
	solib_aix_free_library_list, solib_aix_parse_libraries,
	solib_aix_get_library_list,
	solib_aix_relocate_section_addresses, solib_aix_free_so,
	solib_aix_get_section_offsets,
	solib_aix_solib_create_inferior_hook, solib_aix_current_sos):
	Adjust.
	(struct solib_aix_inferior_data) <library_list>: Adjust.
	* solib-darwin.c (struct lm_info): Rename to ...
	(struct lm_info_darwin): ... this.  Extend lm_info_base.
	(darwin_current_sos, darwin_relocate_section_addresses): Adjust.
	* solib-dsbt.c (struct lm_info): Rename to ...
	(struct lm_info_dsbt): ... this.  Extend lm_info_base.
	(struct dsbt_info) <main_executable_lm_info): Adjust.
	(dsbt_current_sos, dsbt_relocate_main_executable, dsbt_free_so,
	dsbt_relocate_section_addresses): Adjust.
	* solib-frv.c (struct lm_info): Rename to ...
	(struct lm_info_frv): ... this.  Extend lm_info_base.
	(main_executable_lm_info): Adjust.
	(frv_current_sos, frv_relocate_main_executable, frv_free_so,
	frv_relocate_section_addresses, frv_fdpic_find_global_pointer,
	find_canonical_descriptor_in_load_object,
	frv_fdpic_find_canonical_descriptor): Adjust.
	* solib-svr4.c (struct lm_info): Move to solib-svr4.h, renamed
	to lm_info_svr4.
	(lm_info_read, lm_addr_check, svr4_keep_data_in_core,
	svr4_clear_so, svr4_copy_library_list,
	library_list_start_library, svr4_default_sos, svr4_read_so_list,
	svr4_current_sos, svr4_fetch_objfile_link_map,
	solist_update_incremental): Adjust.
	* solib-svr4.h (struct lm_info_svr4): Move here from
	solib-svr4.c.
	* solib-target.c (struct lm_info): Rename to ...
	(struct lm_info_target): ... this.  Extend lm_info_base.
	(lm_info_p): Rename to ...
	(lm_info_target_p): ... this.
	(solib_target_parse_libraries, library_list_start_segment,
	library_list_start_section, library_list_start_library,
	library_list_end_library, solib_target_free_library_list,
	solib_target_current_sos, solib_target_free_so,
	solib_target_relocate_section_addresses): Adjust.
	* windows-nat.c (struct lm_info): Rename to ...
	(struct lm_info_windows): ... this.  Extend lm_info_base.
	(windows_make_so, handle_load_dll, handle_unload_dll,
	windows_xfer_shared_libraries): Adjust.

gdb/nto-tdep.c

@@ -239,43 +239,12 @@ nto_parse_redirection (char *pargv[], const char **pin, const char **pout,
   return argv;
 }
 
-/* The struct lm_info, lm_addr, and nto_truncate_ptr are copied from
-   solib-svr4.c to support nto_relocate_section_addresses
-   which is different from the svr4 version.  */
-
-/* Link map info to include in an allocated so_list entry */
-
-struct lm_info
-  {
-    /* Pointer to copy of link map from inferior.  The type is char *
-       rather than void *, so that we may use byte offsets to find the
-       various fields without the need for a cast.  */
-    gdb_byte *lm;
-
-    /* Amount by which addresses in the binary should be relocated to
-       match the inferior.  This could most often be taken directly
-       from lm, but when prelinking is involved and the prelink base
-       address changes, we may need a different offset, we want to
-       warn about the difference and compute it only once.  */
-    CORE_ADDR l_addr;
-
-    /* The target location of lm.  */
-    CORE_ADDR lm_addr;
-  };
-
-
 static CORE_ADDR
 lm_addr (struct so_list *so)
 {
-  if (so->lm_info->l_addr == (CORE_ADDR)-1)
-    {
-      struct link_map_offsets *lmo = nto_fetch_link_map_offsets ();
-      struct type *ptr_type = builtin_type (target_gdbarch ())->builtin_data_ptr;
+  lm_info_svr4 *li = (lm_info_svr4 *) so->lm_info;
 
-      so->lm_info->l_addr =
-	extract_typed_address (so->lm_info->lm + lmo->l_addr_offset, ptr_type);
-    }
-  return so->lm_info->l_addr;
+  return li->l_addr;
 }
 
 static CORE_ADDR