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

src/version.cpp

@@ -39,13 +39,11 @@ const std::string CLIENT_NAME("Satoshi");
 #    define GIT_COMMIT_DATE "$Format:%cD"
 #endif
 
-#define STRINGIFY(s) #s
-
 #define BUILD_DESC_FROM_COMMIT(maj,min,rev,build,commit) \
-    "v" STRINGIFY(maj) "." STRINGIFY(min) "." STRINGIFY(rev) "." STRINGIFY(build) "-g" commit
+    "v" DO_STRINGIZE(maj) "." DO_STRINGIZE(min) "." DO_STRINGIZE(rev) "." DO_STRINGIZE(build) "-g" commit
 
 #define BUILD_DESC_FROM_UNKNOWN(maj,min,rev,build) \
-    "v" STRINGIFY(maj) "." STRINGIFY(min) "." STRINGIFY(rev) "." STRINGIFY(build) "-unk"
+    "v" DO_STRINGIZE(maj) "." DO_STRINGIZE(min) "." DO_STRINGIZE(rev) "." DO_STRINGIZE(build) "-unk"
 
 #ifndef BUILD_DESC
 #    ifdef GIT_COMMIT_ID