Case insensitive file assumption for OS X

[Ioan Chera]

In file.cpp, there's this part:

FString File::getInsensitiveFile(const FString &filename, bool sensitiveExtension) const
{
#if defined(WINDOWS) || defined(__APPLE__)
    // Insensitive filesystem, so just return the filename
    return filename;
#else

which assumes that file systems are case insensitive on Windows or Mac OS X. I don't know about Windows, but OS X also supports case sensitive file systems if you format the volume that way.

[Braden Obrzut]

Case sensitive file systems should be fully supported in changeset dc8bdcc, but my Mac is formatted insensitive so I'm not entirely sure it works.