Improved and portable ast_log recursion avoidance

This introduces a new logger routine ast_log_safe.  This routine should be
used for all error messages in code that can be run as a result of ast_log.
ast_log_safe does nothing if run recursively.  All error logging in
astobj2.c, strings.c and utils.h have been switched to ast_log_safe.

This required adding support for raw threadstorage.  This provides direct
access to the void* pointer in threadstorage.  In ast_log_safe, NULL is used
to signify that this thread is not already running ast_log_safe, (void*)1 when
it is already running.  This was done since it's critical that ast_log_safe
do nothing that could log during recursion checking.

ASTERISK-24155 #close
Reported by: Timo Teräs
Review: https://reviewboard.asterisk.org/r/4502/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@433522 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/astobj2.c

@@ -33,6 +33,9 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #include "asterisk/cli.h"
 #include "asterisk/paths.h"
 
+/* Use ast_log_safe in place of ast_log. */
+#define ast_log ast_log_safe
+
 #if defined(TEST_FRAMEWORK)
 /* We are building with the test framework enabled so enable AO2 debug tests as well. */
 #define AO2_DEBUG 1