#80 better DirectWrite 2 support

[sav]

Hi, Everyone,

Got errors 'DWRITE_E_NOCOLOR' was not declared in this scope, 'IDWriteFontFace2' was not declared in this scope, etc. while building some code with Mingw-w64 5.3.0, which uses dwrite_2.h functionality.
Could anyone give insight, whether futher implementation of DirectWrite 2 panned in future versions of Mingw-w64? Since it was already implemented in Wine (see https://github.com/wine-mirror/wine/blob/master/include/dwrite_2.idl).

Regards,
Alexander