Merge some file writing extension checks from OpenJK.

Thanks Ensiform.
https://github.com/JACoders/OpenJK/commit/05928a57f9e4aae15a3bd0
https://github.com/JACoders/OpenJK/commit/ef124fd0fc48af164581176
int QDECL Com_strCompare( const void *a, const void *b )
{
    const char **pa = (const char **)a;
    const char **pb = (const char **)b;
    return strcmp( *pa, *pb );
}

int QDECL Com_strCompare( const void *a, const void *b )
{
    const char **pa = (const char **)a;
    const char **pb = (const char **)b;
    return strcmp( *pa, *pb );
}
