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/Q3D/Q3DLoader.cpp

@@ -92,7 +92,7 @@ bool Q3DImporter::CanRead(const std::string &pFile, IOSystem *pIOHandler, bool c
     else if (!extension.length() || checkSig) {
         if (!pIOHandler)
             return true;
-        const char *tokens[] = { "quick3Do", "quick3Ds" };
+        static const char * const tokens[] = { "quick3Do", "quick3Ds" };
         return SearchFileHeaderForToken(pIOHandler, pFile, tokens, 2);
     }
     return false;