Refactor utility/decomp headers (#318)

util/compat.h

@@ -0,0 +1,28 @@
+#ifndef COMPAT_H
+#define COMPAT_H
+
+// Various macros to enable compiling with other/newer compilers.
+
+// Use `COMPAT_CONST` where something ought to be 'const', and a newer compiler would complain if it
+// wasn't, but we know it isn't 'const' in the original code.
+#ifdef __MINGW32__
+#define COMPAT_CONST const
+#else
+#define COMPAT_CONST
+#endif
+
+// Disable "identifier was truncated to '255' characters" warning.
+// Impossible to avoid this if using STL map or set.
+// This removes most (but not all) occurrences of the warning.
+#pragma warning(disable : 4786)
+
+#define MSVC420_VERSION 1020
+
+// We use `override` so newer compilers can tell us our vtables are valid,
+// however this keyword was added in C++11, so we define it as empty for
+// compatibility with older compilers.
+#if defined(_MSC_VER) && _MSC_VER <= 1200 // 1200 corresponds to VC6.0 but "override" was probably added even later
+#define override
+#endif
+
+#endif // COMPAT_H