Not all systems use st_[cm]tim field for ns resolution file timestamp

Some codepaths do not still use the ST_[CM]TIME_NSEC() pair of macros
introduced by the previous commit but assumes all systems use st_mtim
and st_ctim fields in "struct stat" to record nanosecond resolution part
of the file timestamps.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-fetch-pack.c

@@ -807,7 +807,7 @@ struct ref *fetch_pack(struct fetch_pack_args *my_args,
 				die("shallow file was removed during fetch");
 		} else if (st.st_mtime != mtime.sec
 #ifdef USE_NSEC
-				|| st.st_mtim.tv_nsec != mtime.nsec
+				|| ST_CTIME_NSEC(st) != mtime.nsec
 #endif
 			  )
 			die("shallow file was changed during fetch");

read-cache.c

@@ -204,9 +204,9 @@ static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
 		changed |= CTIME_CHANGED;
 
 #ifdef USE_NSEC
-	if (ce->ce_mtime.nsec != (unsigned int)st->st_mtim.tv_nsec)
+	if (ce->ce_mtime.nsec != ST_MTIME_NSEC(*st))
 		changed |= MTIME_CHANGED;
-	if (trust_ctime && ce->ce_ctime.nsec != (unsigned int)st->st_ctim.tv_nsec)
+	if (trust_ctime && ce->ce_ctime.nsec != ST_CTIME_NSEC(*st))
 		changed |= CTIME_CHANGED;
 #endif