more const in format detection

BaseImporter::SearchFileHeaderForToken() expected a pointer to a non-const token list. This was probably an oversight, as nobody would realistically expect the function to change the list. Furthermore, it prevented token lists from being compiled to read-only memory, in some cases even causing the compiler to generate thread-safe initialization.

The list is now const and all callers declare their token lists static const, thus compiling them to read-only memory.

code/AssetLib/XGL/XGLLoader.cpp

@@ -118,7 +118,7 @@ bool XGLImporter::CanRead(const std::string &pFile, IOSystem *pIOHandler, bool c
 	} else if (extension == "xml" || checkSig) {
 		ai_assert(pIOHandler != NULL);
 
-		const char *tokens[] = { "<world>", "<World>", "<WORLD>" };
+		static const char * const tokens[] = { "<world>", "<World>", "<WORLD>" };
 		return SearchFileHeaderForToken(pIOHandler, pFile, tokens, 3);
 	}
 	return false;