implement MZ_DO_NOT_INLINE() for MSVC

For 64-bit builds, MSVC has become smart enough to inline functions
in a way that interferes with the implementation of continuations,
so that (planet "williams/simulation/examples/model-2b") crashes,
for example. Explicitly disabling inlining avoids the problem by
making the C stack layout match the implementation's expectation.

src/racket/src/schpriv.h

@@ -120,6 +120,8 @@ int scheme_num_types(void);
 
 #if MZ_USE_NOINLINE
 # define MZ_DO_NOT_INLINE(decl) decl __attribute__ ((noinline));
+#elif _MSC_VER
+# define MZ_DO_NOT_INLINE(decl) __declspec(noinline) decl;
 #else
 # define MZ_DO_NOT_INLINE(decl)
 #endif