util: drop UID_IS_INVALID() in favour of uid_is_valid()

No need to keep both functions, settle on uid_is_valid() for everything.

src/basic/macro.h

@@ -470,18 +470,6 @@ do {                                                                    \
 #define GID_INVALID ((gid_t) -1)
 #define MODE_INVALID ((mode_t) -1)
 
-static inline bool UID_IS_INVALID(uid_t uid) {
-        /* We consider both the old 16bit -1 user and the newer 32bit
-         * -1 user invalid, since they are or used to be incompatible
-         * with syscalls such as setresuid() or chown(). */
-
-        return uid == (uid_t) ((uint32_t) -1) || uid == (uid_t) ((uint16_t) -1);
-}
-
-static inline bool GID_IS_INVALID(gid_t gid) {
-        return gid == (gid_t) ((uint32_t) -1) || gid == (gid_t) ((uint16_t) -1);
-}
-
 #define DEFINE_TRIVIAL_CLEANUP_FUNC(type, func)                 \
         static inline void func##p(type *p) {                   \
                 if (*p)                                         \

src/basic/util.h

@@ -161,7 +161,10 @@ int parse_uid(const char *s, uid_t* ret_uid);
 #define parse_gid(s, ret_gid) parse_uid(s, ret_gid)
 
 bool uid_is_valid(uid_t uid);
-#define gid_is_valid(gid) uid_is_valid(gid)
+
+static inline bool gid_is_valid(gid_t gid) {
+        return uid_is_valid((uid_t) gid);
+}
 
 int safe_atou(const char *s, unsigned *ret_u);
 int safe_atoi(const char *s, int *ret_i);