Generate windows version automatically

[unknownbrackets]

NOTE: This makes the assumption that from now on, we'll stick with "x.y.z" versioning. That means if we use 1.0.1.1 or 1.0.2.5, it will break. Personally I think this is reasonable. Logarithmic versions don't help us or anyone else. A new version is a new version.

This allows for the same customization git-version.cpp allows.

Also, it improves messaging slightly during build if git is missing, and disallows reporting for builds generated without version info to make it clearer to users of such builds.

The changes to version.rc:

@@ -1,9 +1,12 @@

-//This file is encoded in UTF-16, which is not supported by git. It is included in ppsspp.rc with "include".
+// This file is encoded in UTF-16, which is not supported by git. It is included in ppsspp.rc with "include".
+
+// win-version.h is generated by git-version-gen.cmd.
+#include "win-version.h"

 VS_VERSION_INFO VERSIONINFO
- FILEVERSION 1,0,1,0
- PRODUCTVERSION 1,0,1,0
+ FILEVERSION PPSSPP_WIN_VERSION_COMMA
+ PRODUCTVERSION PPSSPP_WIN_VERSION_COMMA
  FILEFLAGSMASK 0x17L
 #ifdef _DEBUG
  FILEFLAGS 0x1L
@@ -21,13 +24,13 @@
             VALUE "Comments", "PPSSPP PSP emulator"
             VALUE "CompanyName", "Henrik Rydgård"
             VALUE "FileDescription", "PPSSPP"
-            VALUE "FileVersion", "1, 0, 1, 0"
+            VALUE "FileVersion", PPSSPP_WIN_VERSION_STRING
             VALUE "InternalName", "PPSSPPEmu"
             VALUE "LegalCopyright", "Copyright (C) 2006-2015 by Henrik Rydgård"
             VALUE "LegalTrademarks", "All product names are trademarks of their respective owners."
             VALUE "OriginalFilename", "PPSSPP.exe"
             VALUE "ProductName", "PPSSPP"
-            VALUE "ProductVersion", "1, 0, 1, 0"
+            VALUE "ProductVersion", PPSSPP_WIN_VERSION_STRING
         END
     END
     BLOCK "VarFileInfo"

Closes #6406. This is really just an update of that pull to some degree.

-[Unknown]