[FIX] Addding required include for ptrdiff_t.

Was missing, triggered by C++11 mode of MinGW 4.7.2.
[FIX] Using manual implementation of isblank() in MinGW.

MinGW 4.7.2 does not find this function in C++11 mode.
[FIX] Using tmpnam() instead of _tempnam() in MinGW.

The C++11 mode of MinGW 4.7.2 does not find the symbol _tempnam().
Merge pull request #100 from holtgrewe/hotfix/razers3_mingw_fix

Making RazerS 3 compile on MinGW.