MSVC: Show compiler version in AboutDialog

Make AboutDialog support MSVC compiler info so we can use a screenshot of
it to brag with on #devtalk

include/versioninfo.h

@@ -1,7 +1,11 @@
+#include "lmms_basics.h"
+
 #ifdef __GNUC__
-#define GCC_VERSION "GCC " __VERSION__
+#define COMPILER_VERSION "GCC " __VERSION__
+#elif defined(_MSC_VER)
+#define COMPILER_VERSION "MSVC " STRINGIFY(_MSC_FULL_VER)
 #else
-#define GCC_VERSION "unknown compiler"
+#define COMPILER_VERSION "unknown compiler"
 #endif
 
 #ifdef LMMS_HOST_X86

src/core/main.cpp

@@ -130,7 +130,7 @@ void printVersion( char *executableName )
 		"License as published by the Free Software Foundation; either\n"
 		"version 2 of the License, or (at your option) any later version.\n\n"
 		"Try \"%s --help\" for more information.\n\n", LMMS_VERSION,
-		PLATFORM, MACHINE, QT_VERSION_STR, GCC_VERSION,
+		PLATFORM, MACHINE, QT_VERSION_STR, COMPILER_VERSION,
 		LMMS_PROJECT_COPYRIGHT, executableName );
 }
 

src/gui/AboutDialog.cpp

@@ -44,7 +44,7 @@ AboutDialog::AboutDialog(QWidget* parent) :
 					arg( PLATFORM ).
 					arg( MACHINE ).
 					arg( QT_VERSION_STR ).
-					arg( GCC_VERSION ) );
+					arg( COMPILER_VERSION ) );
 	versionLabel->setTextInteractionFlags(
 					versionLabel->textInteractionFlags() |
 					Qt::TextSelectableByMouse );