Remove ATL dependency so VC++ Express can build

The Express editions of Visual C++ ship without ATL. The only ATL usage was
in MUNGA_L4/L4APP.cpp (atlbase.h/atlconv.h + USES_CONVERSION/W2A macros, all
in that one file) for wide-to-ANSI conversion of command-line arguments.

- Replace the ATL includes with a self-contained L4WideToAnsi helper (a
  WideCharToMultiByte wrapper) and local USES_CONVERSION/W2A macros that
  reproduce ATL's W2A semantics. All call sites consume the result immediately
  (stricmp / CString assignment / atoi / atol), so behaviour is unchanged.
- Set UseOfATL="0" in Munga_L4.vcproj, RP_L4.vcproj and their VS2008 variants.
- Document the Express build path and the confirmed June 2010 DirectX SDK in
  BUILD.md (new section 6) and docs/BUILD-NOTES.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

MUNGA_L4/L4APP.cpp

@@ -13,8 +13,45 @@
 #include "l4mppr.h"
 #include "..\munga\player.h"
 #include "..\munga\mission.h"
-#include <atlbase.h>
-#include <atlconv.h>
+//
+// Minimal stand-in for ATL's <atlconv.h> USES_CONVERSION / W2A macros.
+// VC++ Express and the Windows SDK do not ship ATL, and the only ATL feature
+// this file used was wide-to-ANSI conversion of command-line tokens below.
+// L4WideToAnsi mirrors ATL's W2A semantics: each use produces an independent
+// buffer that stays valid until the end of the enclosing full-expression.
+//
+namespace
+{
+	class L4WideToAnsi
+	{
+	public:
+		explicit L4WideToAnsi(const wchar_t* wide) : mBuffer(0)
+		{
+			int needed = (wide != 0)
+				? ::WideCharToMultiByte(CP_ACP, 0, wide, -1, 0, 0, 0, 0)
+				: 0;
+			if (needed <= 0)
+			{
+				needed = 1;
+			}
+			mBuffer = new char[needed];
+			if (wide == 0 ||
+				::WideCharToMultiByte(CP_ACP, 0, wide, -1, mBuffer, needed, 0, 0) <= 0)
+			{
+				mBuffer[0] = '\0';
+			}
+		}
+		~L4WideToAnsi() { delete [] mBuffer; }
+		operator char*() { return mBuffer; }
+	private:
+		char* mBuffer;
+		L4WideToAnsi(const L4WideToAnsi&);				// non-copyable
+		L4WideToAnsi& operator=(const L4WideToAnsi&);
+	};
+}
+
+#define USES_CONVERSION	((void)0)
+#define W2A(w)			(static_cast<char*>(L4WideToAnsi(w)))
 
 L4Application*&
 	l4_application = (L4Application*&)application;