* grp.cc (getgrent32): Only refresh group entries when at beginning.

(internal_getgrsid): Only refresh if uninitialized.
(internal_getgrent): Ditto.
* passwd.cc (getpwent): Only refresh passwd entries when at beginning.
(pwdgrp::read_passwd): linebuf *cannot* be NO_COPY.
(internal_getpwsid): Only refresh if uninitialized.
(getpass): No need to refresh passwd data here.
* pwdgrp.h (refresh): Eliminate default.

winsup/cygwin/pwdgrp.h

@@ -67,7 +67,7 @@ public:
   int curr_lines;
 
   void load (const char *);
-  void refresh (bool check = true)
+  void refresh (bool check)
   {
     if (!check && initialized)
       return;