Core: Fix a few compile warnings

src/tools/map_extractor/loadlib.cpp

@@ -49,7 +49,7 @@ bool FileLoader::prepareLoadedData()
 {
     // Check version
     version = (file_MVER *) data;
-    if (version->fcc != 'MVER')
+    if (version->fcc != "MVER")
         return false;
     if (version->ver != FILE_FORMAT_VERSION)
         return false;