misc: Improve error handling

Remove calls to generic error handler or use stderr for

- legacy deprecation warnings
- nanohttp, nanoftp in standalone mode
- memory debug messages

Use xmlRaiseMemoryError.

Remove TODO macro.

Don't raise errors in xmlmodule.c.

threads.c

@@ -498,9 +498,8 @@ xmlGlobalInitMutexLock(void) {
     if (global_init_lock == NULL) {
         cs = malloc(sizeof(CRITICAL_SECTION));
         if (cs == NULL) {
-            xmlGenericError(xmlGenericErrorContext,
-                            "xmlGlobalInitMutexLock: out of memory\n");
-            return;
+            fprintf(stderr, "libxml2: xmlInitParser: out of memory\n");
+            abort();
         }
         InitializeCriticalSection(cs);