Move m_typeof to core module.

m-core.h

@@ -142,7 +142,6 @@
 # define M_ATTR_COLD_FUNCTION
 #endif
 
-
 /* Prefetch . */
 #if defined(__GNUC__)
 # define M_PREFETCH(p)           __builtin_prefetch((p), 0, 0)
@@ -153,6 +152,17 @@
   } while (0)
 #endif
 
+/* Definition of the typeof keyword
+   In C23, we can use the standard keyword.
+   Otherwise we use some extensions of the compilers. */
+#ifdef _MSC_VER
+#define m_typeof(x) decltype(x)
+#elif defined(__GNUC__)   
+#define m_typeof(x) __typeof__(x)
+#else
+#define m_typeof(x) typeof(x)
+#endif
+
 /* Ignore some warnings detected by some compilers in the library.
  * Whatever we do, there is some warnings that cannot be fixed.
  * So they are ignored in order to avoid polluting the user with