Add static assert to catch errors in COPY(a,b)

Marlin/src/core/macros.h

 #define DECIMAL_SIGNED(a) (DECIMAL(a) || (a) == '-' || (a) == '+')
 #define COUNT(a) (sizeof(a)/sizeof(*a))
 #define ZERO(a) memset(a,0,sizeof(a))
-#define COPY(a,b) memcpy(a,b,MIN(sizeof(a),sizeof(b)))
+#define COPY(a,b) do{ \
+    static_assert(sizeof(a[0]) == sizeof(b[0]), "COPY: '" STRINGIFY(a) "' and '" STRINGIFY(b) "' types (sizes) don't match!"); \
+    memcpy(&a[0],&b[0],MIN(sizeof(a),sizeof(b))); \
+  }while(0)
 
 // Macros for initializing arrays
 #define ARRAY_6(v1, v2, v3, v4, v5, v6, ...) { v1, v2, v3, v4, v5, v6 }