remove msymbol_objfile

This is another patch in my ongoing series to "split" objfile to share
more read-only data across inferiors.  See

    http://sourceware.org/gdb/wiki/ObjfileSplitting

When symbols are finally shared, there will be no back-link from the
symbol to its containing objfile, because there may be more than one
such objfile.  So, all such back-links must be removed.

One hidden back-link is the msymbol_objfile function.  Since
(eventually) a symbol may appear in more than one objfile, trying to
look up the objfile given just a symbol cannot work.

This patch removes msymbol_objfile in favor of using a bound minimal
symbol.  It introduces a new function to make this conversion simpler
in some spots.

The bonus of this patch is that using msymbol_objfile is slower than
simply looking up the owning objfile in the first place.

Built and regtested on x86-64 Fedora 18.

	* ada-exp.y (write_var_or_type): Use bound_minimal_symbol.
	* ada-lang.c (ada_lookup_simple_minsym): Return
	bound_minimal_symbol.
	* ada-lang.h (ada_lookup_simple_minsym): Update.
	* c-exp.y (variable): Use lookup_bound_minimal_symbol.
	* f-exp.y (variable): Use lookup_bound_minimal_symbol.
	* go-exp.y (variable): Use lookup_bound_minimal_symbol.
	* jv-exp.y (push_expression_name): Use lookup_bound_minimal_symbol.
	* m2-exp.y (variable): Use lookup_bound_minimal_symbol.
	* minsyms.c (msymbol_objfile): Remove.
	(lookup_minimal_symbol_internal): New function, from
	lookup_minimal_symbol.
	(lookup_minimal_symbol): Rewrite using
	lookup_minimal_symbol_internal.
	(lookup_bound_minimal_symbol): New function.
	* minsyms.h (msymbol_objfile): Remove.
	(lookup_bound_minimal_symbol): Declare.
	* p-exp.y (variable): Use lookup_bound_minimal_symbol.
	* parse.c (write_exp_msymbol): Change parameter to a
	bound_minimal_symbol.
	(write_dollar_variable): Use lookup_bound_minimal_symbol.
	* parser-defs.h (write_exp_msymbol): Update.
	* printcmd.c (address_info): Use lookup_bound_minimal_symbol.
	* symfile.c (simple_read_overlay_table): Use
	lookup_bound_minimal_symbol.
	* symtab.c (skip_prologue_sal): Don't use msymbol_objfile.
	(search_symbols): Likewise.
	(print_msymbol_info): Take a bound_minimal_symbol argument.
	(symtab_symbol_info, rbreak_command): Update.
	* symtab.h (struct symbol_search) <msymbol>: Change type
	to bound_minimal_symbol.
	* valops.c (find_function_in_inferior): Use
	lookup_bound_minimal_symbol.
	* value.c (value_fn_field): Use lookup_bound_minimal_symbol.

gdb/ada-lang.c

@@ -4405,18 +4405,22 @@ defns_collected (struct obstack *obstackp, int finish)
     return (struct ada_symbol_info *) obstack_base (obstackp);
 }
 
-/* Return a minimal symbol matching NAME according to Ada decoding
-   rules.  Returns NULL if there is no such minimal symbol.  Names
-   prefixed with "standard__" are handled specially: "standard__" is
-   first stripped off, and only static and global symbols are searched.  */
+/* Return a bound minimal symbol matching NAME according to Ada
+   decoding rules.  Returns an invalid symbol if there is no such
+   minimal symbol.  Names prefixed with "standard__" are handled
+   specially: "standard__" is first stripped off, and only static and
+   global symbols are searched.  */
 
-struct minimal_symbol *
+struct bound_minimal_symbol
 ada_lookup_simple_minsym (const char *name)
 {
+  struct bound_minimal_symbol result;
   struct objfile *objfile;
   struct minimal_symbol *msymbol;
   const int wild_match_p = should_use_wild_match (name);
 
+  memset (&result, 0, sizeof (result));
+
   /* Special case: If the user specifies a symbol name inside package
      Standard, do a non-wild matching of the symbol name without
      the "standard__" prefix.  This was primarily introduced in order
@@ -4431,10 +4435,14 @@ ada_lookup_simple_minsym (const char *name)
   {
     if (match_name (SYMBOL_LINKAGE_NAME (msymbol), name, wild_match_p)
         && MSYMBOL_TYPE (msymbol) != mst_solib_trampoline)
-      return msymbol;
+      {
+	result.minsym = msymbol;
+	result.objfile = objfile;
+	break;
+      }
   }
 
-  return NULL;
+  return result;
 }
 
 /* For all subprograms that statically enclose the subprogram of the