Fix memory corruption when trying to get "core show locks".

Review https://reviewboard.asterisk.org/r/2580/ tried to fix the mismatch
in memory pools but had a math error determining the buffer size and
didn't address other similar memory pool mismatches.

* Effectively reverted the previous patch to go in the same direction as
trunk for the returned memory pool of ast_bt_get_symbols().

* Fixed memory leak in ast_bt_get_symbols() when BETTER_BACKTRACES is
defined.

* Fixed some formatting in ast_bt_get_symbols().

* Fixed sig_pri.c freeing memory allocated by libpri when MALLOC_DEBUG is
enabled.

* Fixed __dump_backtrace() freeing memory from ast_bt_get_symbols() when
MALLOC_DEBUG is enabled.

* Moved __dump_backtrace() because of compile issues with the utils
directory.

(closes issue ASTERISK-22221)
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/2778/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@397525 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/astobj2.c

@@ -98,7 +98,7 @@ void ao2_bt(void)
 	for(i = 0; i < c; i++) {
 		ast_verbose("%d: %p %s\n", i, addresses[i], strings[i]);
 	}
-	ast_free(strings);
+	ast_std_free(strings);
 }
 #endif