Allow proper serialization of size_t in marsh.c

Typed arrays used size_t in serialization: C APIs will
also often use it, so it makes sense to add first class support
for it rather than assume it will will fint into an integer.

These changes should quiet some visual studio warnings.

Also make some spacing more consistent.

src/core/util.h

@@ -93,6 +93,4 @@ void janet_lib_peg(JanetTable *env);
 void janet_lib_typed_array(JanetTable *env);
 #endif
 
-
-
 #endif