Remove unused variable that is shadowed by another one later
Fix warning about unused vaiable in release mode
Fix warning from SFMT library

Usually I don't like tinkering with 3rd-party code, but this
warning is very annoying and rather useless. It's only there
to say that a sensible default value was chosen, which is
nothing to be worried about.
Fix warning about missing function prototype
Fix ARC detection preprocessor directive
Simplify ARC macro definitions
Merge pull request #756 from theGoodEvil/fix_warnings

Fix Warnings in Xcode Builds