pbx: Fix lack of cleanup on macrolock and context_table

(closes issue ASTERISK-21723)
Reported by: Corey Farrell
Patches:
    core-pbx-cleanup.patch uploaded by Correy Farrell (license 5909)
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Merged revisions 388532 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 388578 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@388579 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/pbx.c

@@ -10435,6 +10435,7 @@ static void __ast_internal_context_destroy( struct ast_context *con)
 	}
 	tmp->root = NULL;
 	ast_rwlock_destroy(&tmp->lock);
+	ast_mutex_destroy(&tmp->macrolock);
 	ast_free(tmp);
 }
 
@@ -12142,6 +12143,10 @@ static void pbx_shutdown(void)
 		ao2_ref(statecbs, -1);
 		statecbs = NULL;
 	}
+	if (contexts_table) {
+		ast_hashtab_destroy(contexts_table, NULL);
+	}
+	pbx_builtin_clear_globals();
 }
 
 int ast_pbx_init(void)