This extends #1607, which got recently merged, with version information for bitcoin-qt.exe (no additional files need to be modified by hand).
- add version information to bitcoin-qt.rc, which is displayed on Windows, when looking in the executable properties and selecting "Details"
- introduce a new clientversion.h (used in bitcoin-qt.rc to generate version information), which takes only the version defines from version.h and is included in it (to allow usage with the windres rc-file compiler)
- move #define STRINGIFY(s) #s into clientversion.h as that is used in bitcoin-qt.rc and rename to DO_STRINGIZE(X)
- add #define STRINGIZE(X) DO_STRINGIZE(X), which is needed to convert the version defines into a version string in the rc-file
- this ensures we only need to update 1 file and have bitcoin-qt.exe version information
- for RC-file documentation see: http://msdn.microsoft.com/en-us/library/windows/desktop/aa381058%28v=vs.85%29.aspx
