time: explicitly size the time macros

The default backing for `enum` types on Windows are signed values, and
the enumerators are handled via integer promotion to the type.
Explicitly type the enums to ensure that the type is correct.

Author: compnerd

dispatch/time.h

@@ -66,7 +66,7 @@ struct timespec;
  */
 typedef uint64_t dispatch_time_t;
 
-enum {
+enum : unsigned long long {
 	DISPATCH_WALLTIME_NOW DISPATCH_ENUM_API_AVAILABLE(macos(10.14), ios(12.0), tvos(12.0), watchos(5.0))	= ~1ull,
 };
 

private/time_private.h

@@ -49,7 +49,7 @@ __BEGIN_DECLS
  * dispatch_source_set_timer(ds, t, 10 * NSEC_PER_SEC, 0);
  * dispatch_activate(ds);
  */
-enum {
+enum : unsigned long long {
 	DISPATCH_MONOTONICTIME_NOW DISPATCH_ENUM_API_AVAILABLE(macos(10.14), ios(12.0), tvos(12.0), watchos(5.0)) = (1ull << 63)
 };