Replace X-allocation functions with their C89 counterparts

The only remaining X-functions used in server are XNF*, the rest is converted to
plain alloc/calloc/realloc/free/strdup.

X* functions are still exported from server and x* macros are still defined in
header file, so both ABI and API are not affected by this change.

Signed-off-by: Mikhail Gusarov <dottedmag@dottedmag.net>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>

os/xprintf.c

@@ -54,7 +54,7 @@ Xvprintf(const char *format, va_list va)
     size = vsnprintf(NULL, 0, format, va2);
     va_end(va2);
 
-    ret = (char *)Xalloc(size + 1);
+    ret = (char *)malloc(size + 1);
     if (ret == NULL)
         return NULL;