util.c: move printuid to uid.c

This will make further uid/gid fixes simpler.

* util.c (printuid): Move
* uid.c: ... here.
diff --git a/uid.c b/uid.c
index 0991074..0a1a2ee 100644
--- a/uid.c
+++ b/uid.c
@@ -75,3 +75,12 @@
 	}
 	return 0;
 }
+
+void
+printuid(const char *text, const unsigned int uid)
+{
+	if ((unsigned int) -1 == uid)
+		tprintf("%s-1", text);
+	else
+		tprintf("%s%u", text, uid);
+}