Minor Linux build issues

[MarkLeone]

There are case-sensitive filename mismatches in the CMake file:
3rdParty should be "3rdparty" and "Config.h" should be "config.h".

gcc 9.4 rejects using the same name for an enum class and a corresponding struct member:
GDeflateDemo/main.cpp:62:15: error: declaration of ‘Operation Options::Operation’ changes meaning of ‘Operation’

I will submit a pull request that fixes these.