Convert observers to C++

This converts observers from using a special source-generating script
to be plain C++.  This version of the patch takes advantage of C++11
by using std::function and variadic templates; incorporates Pedro's
patches; and renames the header file to "observable.h" (this change
eliminates the need for a clean rebuild).

Note that Pedro's patches used a template lambda in tui-hooks.c, but
this failed to compile on some buildbot instances (presumably due to
differing C++ versions); I replaced this with an ordinary template
function.

Regression tested on the buildbot.

gdb/ChangeLog
2018-03-19  Pedro Alves  <palves@redhat.com>
	    Tom Tromey  <tom@tromey.com>

	* unittests/observable-selftests.c: New file.
	* common/observable.h: New file.
	* observable.h: New file.
	* ada-lang.c, ada-tasks.c, agent.c, aix-thread.c, annotate.c,
	arm-tdep.c, auto-load.c, auxv.c, break-catch-syscall.c,
	breakpoint.c, bsd-uthread.c, cli/cli-interp.c, cli/cli-setshow.c,
	corefile.c, dummy-frame.c, event-loop.c, event-top.c, exec.c,
	extension.c, frame.c, gdbarch.c, guile/scm-breakpoint.c,
	infcall.c, infcmd.c, inferior.c, inflow.c, infrun.c, jit.c,
	linux-tdep.c, linux-thread-db.c, m68klinux-tdep.c,
	mi/mi-cmd-break.c, mi/mi-interp.c, mi/mi-main.c, objfiles.c,
	ppc-linux-nat.c, ppc-linux-tdep.c, printcmd.c, procfs.c,
	python/py-breakpoint.c, python/py-finishbreakpoint.c,
	python/py-inferior.c, python/py-unwind.c, ravenscar-thread.c,
	record-btrace.c, record-full.c, record.c, regcache.c, remote.c,
	riscv-tdep.c, sol-thread.c, solib-aix.c, solib-spu.c, solib.c,
	spu-multiarch.c, spu-tdep.c, stack.c, symfile-mem.c, symfile.c,
	symtab.c, thread.c, top.c, tracepoint.c, tui/tui-hooks.c,
	tui/tui-interp.c, valops.c: Update all users.
	* tui/tui-hooks.c (tui_bp_created_observer)
	(tui_bp_deleted_observer, tui_bp_modified_observer)
	(tui_inferior_exit_observer, tui_before_prompt_observer)
	(tui_normal_stop_observer, tui_register_changed_observer):
	Remove.
	(tui_observers_token): New global.
	(attach_or_detach, tui_attach_detach_observers): New functions.
	(tui_install_hooks, tui_remove_hooks): Use
	tui_attach_detach_observers.
	* record-btrace.c (record_btrace_thread_observer): Remove.
	(record_btrace_thread_observer_token): New global.
	* observer.sh: Remove.
	* observer.c: Rename to observable.c.
	* observable.c (namespace gdb_observers): Define new objects.
	(observer_debug): Move into gdb_observers namespace.
	(struct observer, struct observer_list, xalloc_observer_list_node)
	(xfree_observer_list_node, generic_observer_attach)
	(generic_observer_detach, generic_observer_notify): Remove.
	(_initialize_observer): Update.
	Don't include observer.inc.
	* Makefile.in (generated_files): Remove observer.h, observer.inc.
	(clean mostlyclean): Likewise.
	(observer.h, observer.inc): Remove targets.
	(SUBDIR_UNITTESTS_SRCS): Add observable-selftests.c.
	(COMMON_SFILES): Use observable.c, not observer.c.
	* .gitignore: Remove observer.h.

gdb/doc/ChangeLog
2018-03-19  Tom Tromey  <tom@tromey.com>

	* observer.texi: Remove.

gdb/testsuite/ChangeLog
2018-03-19  Tom Tromey  <tom@tromey.com>

	* gdb.gdb/observer.exp: Remove.

gdb/inferior.c

@@ -26,7 +26,7 @@
 #include "gdbcmd.h"
 #include "gdbthread.h"
 #include "ui-out.h"
-#include "observer.h"
+#include "observable.h"
 #include "gdbcore.h"
 #include "symfile.h"
 #include "environ.h"
@@ -109,7 +109,7 @@ add_inferior_silent (int pid)
       last->next = inf;
     }
 
-  observer_notify_inferior_added (inf);
+  gdb::observers::inferior_added.notify (inf);
 
   if (pid != 0)
     inferior_appeared (inf, pid);
@@ -176,7 +176,7 @@ delete_inferior (struct inferior *todel)
   else
     inferior_list = inf->next;
 
-  observer_notify_inferior_removed (inf);
+  gdb::observers::inferior_removed.notify (inf);
 
   /* If this program space is rendered useless, remove it. */
   if (program_space_empty_p (inf->pspace))
@@ -206,7 +206,7 @@ exit_inferior_1 (struct inferior *inftoex, int silent)
 
   iterate_over_threads (delete_thread_of_inferior, &arg);
 
-  observer_notify_inferior_exit (inf);
+  gdb::observers::inferior_exit.notify (inf);
 
   inf->pid = 0;
   inf->fake_pid_p = 0;
@@ -284,7 +284,7 @@ inferior_appeared (struct inferior *inf, int pid)
   inf->has_exit_code = 0;
   inf->exit_code = 0;
 
-  observer_notify_inferior_appeared (inf);
+  gdb::observers::inferior_appeared.notify (inf);
 }
 
 void
@@ -713,7 +713,7 @@ inferior_command (const char *args, int from_tty)
 	  switch_to_thread (tp->ptid);
 	}
 
-      observer_notify_user_selected_context_changed
+      gdb::observers::user_selected_context_changed.notify
 	(USER_SELECTED_INFERIOR
 	 | USER_SELECTED_THREAD
 	 | USER_SELECTED_FRAME);
@@ -724,7 +724,8 @@ inferior_command (const char *args, int from_tty)
       switch_to_thread (null_ptid);
       set_current_program_space (inf->pspace);
 
-      observer_notify_user_selected_context_changed (USER_SELECTED_INFERIOR);
+      gdb::observers::user_selected_context_changed.notify
+	(USER_SELECTED_INFERIOR);
     }
 }