Avoid suspects casts VARHDRSZ (c.h)

Hi,

In all the static analysis tools I’ve used, there are literally *hundreds* of alerts about a one suspect cast:

64 bits sizet_t -> 32 bits int -> 64 bits size_t
-#define VARHDRSZ ((int32) sizeof(int32))
+#define VARHDRSZ (sizeof(int32))

Is there any special reason for not simplifying this and avoiding these alerts?

Passed 100% with vcregress check and in use in local tests.

regards,

Ranier Vilela