Fix leaks of 'per program space' and 'per inferior' ada task data.

Valgrind reports leaks such as the below.
Fix these leaks by changing ada_tasks_pspace_data_handle
and ada_tasks_inferior_data_handle to use the 'with_cleanup' register variant.

Tested on debian/amd64 natively and under Valgrind.

==26346== 56 bytes in 1 blocks are definitely lost in loss record 631 of 3,249
==26346==    at 0x4C2C4CC: operator new(unsigned long) (vg_replace_malloc.c:344)
==26346==    by 0x38F911: get_ada_tasks_inferior_data(inferior*) (ada-tasks.c:281)
==26346==    by 0x38FA3F: ada_tasks_invalidate_inferior_data (ada-tasks.c:1362)
==26346==    by 0x38FA3F: ada_tasks_new_objfile_observer(objfile*) (ada-tasks.c:1411)
==26346==    by 0x60CBC5: operator() (functional:2127)
==26346==    by 0x60CBC5: notify (observable.h:106)
==26346==    by 0x60CBC5: clear_symtab_users(enum_flags<symfile_add_flag>) (symfile.c:2903)
...

==26346== 104 bytes in 1 blocks are definitely lost in loss record 984 of 3,249
==26346==    at 0x4C2E0BC: calloc (vg_replace_malloc.c:762)
==26346==    by 0x4056F0: xcalloc (common-utils.c:84)
==26346==    by 0x38F8AE: xcnew<ada_tasks_pspace_data> (poison.h:122)
==26346==    by 0x38F8AE: get_ada_tasks_pspace_data(program_space*) (ada-tasks.c:253)
==26346==    by 0x38FA77: ada_tasks_invalidate_pspace_data (ada-tasks.c:1354)
==26346==    by 0x38FA77: ada_tasks_new_objfile_observer(objfile*) (ada-tasks.c:1394)
==26346==    by 0x60CBC5: operator() (functional:2127)
==26346==    by 0x60CBC5: notify (observable.h:106)
...

gdb/ChangeLog
2019-02-18  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* ada-task.c (_initialize_tasks): Use 'with_cleanup' register
	variant for ada_tasks_pspace_data_handle and
	ada_tasks_inferior_data_handle.
	(ada_tasks_pspace_data_cleanup): New function.
	(ada_tasks_inferior_data_cleanup): New function.

Author: Philippe Waroquiers

gdb/ChangeLog

@@ -1,3 +1,11 @@
+2019-02-18  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
+
+	* ada-task.c (_initialize_tasks): Use 'with_cleanup' register
+	variant for ada_tasks_pspace_data_handle and
+	ada_tasks_inferior_data_handle.
+	(ada_tasks_pspace_data_cleanup): New function.
+	(ada_tasks_inferior_data_cleanup): New function.
+
 2019-02-17  Tom Tromey  <tom@tromey.com>
 
 	* macrotab.h (macro_source_fullname): Return a std::string.

gdb/ada-tasks.c

@@ -161,6 +161,15 @@ struct ada_tasks_pspace_data
 /* Key to our per-program-space data.  */
 static const struct program_space_data *ada_tasks_pspace_data_handle;
 
+/* A cleanup routine for our per-program-space data.  */
+static void
+ada_tasks_pspace_data_cleanup (struct program_space *pspace, void *arg)
+{
+  struct ada_tasks_pspace_data *data
+    = (struct ada_tasks_pspace_data *) arg;
+  xfree (data);
+}
+
 /* The kind of data structure used by the runtime to store the list
    of Ada tasks.  */
 
@@ -285,6 +294,15 @@ get_ada_tasks_inferior_data (struct inferior *inf)
   return data;
 }
 
+/* A cleanup routine for our per-inferior data.  */
+static void
+ada_tasks_inferior_data_cleanup (struct inferior *inf, void *arg)
+{
+  struct ada_tasks_inferior_data *data
+    = (struct ada_tasks_inferior_data *) arg;
+  delete data;
+}
+
 /* Return the task number of the task whose thread is THREAD, or zero
    if the task could not be found.  */
 
@@ -1414,8 +1432,12 @@ ada_tasks_new_objfile_observer (struct objfile *objfile)
 void
 _initialize_tasks (void)
 {
-  ada_tasks_pspace_data_handle = register_program_space_data ();
-  ada_tasks_inferior_data_handle = register_inferior_data ();
+  ada_tasks_pspace_data_handle
+    = register_program_space_data_with_cleanup (NULL,
+						ada_tasks_pspace_data_cleanup);
+  ada_tasks_inferior_data_handle
+    = register_inferior_data_with_cleanup (NULL,
+					   ada_tasks_inferior_data_cleanup);
 
   /* Attach various observers.  */
   gdb::observers::normal_stop.attach (ada_tasks_normal_stop_observer);