Bitcoin-Qt (Windows only): add version info to Resource File

- 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

bitcoin-qt.pro

@@ -178,7 +178,8 @@ HEADERS += src/qt/bitcoingui.h \
     src/ui_interface.h \
     src/qt/rpcconsole.h \
     src/version.h \
-    src/netbase.h
+    src/netbase.h \
+    src/clientversion.h
 
 SOURCES += src/qt/bitcoin.cpp src/qt/bitcoingui.cpp \
     src/qt/transactiontablemodel.cpp \