Compile with -Wundef to detect stupid macro typos like "GCC_VER"

This was SVN commit r7756.

build/premake/premake.lua

@@ -173,6 +173,7 @@ function package_set_build_flags()
 				-- "-Wformat=2",		-- (useful sometimes, but a bit noisy, so skip it by default)
 				-- "-Wcast-qual",		-- (useful for checking const-correctness, but a bit noisy, so skip it by default)
 				"-Wnon-virtual-dtor",	-- (sometimes noisy but finds real bugs)
+				"-Wundef",				-- (useful for finding macro name typos)
 
 				-- enable security features (stack checking etc) that shouldn't have
 				-- a significant effect on performance and can catch bugs

source/tools/atlas/GameInterface/Shareable.h

@@ -258,13 +258,13 @@ public:
 		wrapped_type r;
 		r.reserve(size);
 		// (/Wp64 causes a spurious warning here. see https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=253172)
-#if MSC_VERSION
+#ifdef _MSC_VER // (can't use MSC_VERSION here since this file is included by Atlas too)
 #pragma warning(push)
 #pragma warning(disable:4267)
 #endif
 		for (size_t i = 0; i < size; ++i)
 			r.push_back(array[i]._Unwrap());
-#if MSC_VERSION
+#ifdef _MSC_VER
 #pragma warning(pop)
 #endif
 		return r;