* cygheap.cc (init_cygheap::etc_changed): New method to signal

a change in /etc.
	* cygheap.h (struct init_cygheap): Add member `etc_changed_h'
	and method `etc_changed'.
	* grp.cc (enum grp_state): Eliminate.
	(class grp_check): Ditto.
	(group_state): Define as `class pwdgrp_check'.
	(parse_grp): Remeber path and modification time of /etc/group file.
	* passwd.cc (enum_pwd_state): Eliminate.
	(class pwd_check): Ditto.
	(passwd_state): Define as `class pwdgrp_check'.
	(read_etc_passwd): Remember path and modification time of /etc/passwd
	file.
	* pwdgrp.h: New file.
	(enum pwdgrp_state): Substitutes `pwd_state' and `grp_state'.
	(class pwdgrp_check): Substitutes `pwd_check' and `grp_check'.

winsup/cygwin/pwdgrp.h

@@ -0,0 +1,57 @@
+/* pwdgrp.h
+
+   Copyright 2001 Red Hat inc.
+
+   Stuff common to pwd and grp handling.
+
+This file is part of Cygwin.
+
+This software is a copyrighted work licensed under the terms of the
+Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
+details. */
+
+enum pwdgrp_state {
+  uninitialized = 0,
+  initializing,
+  emulated,
+  loaded
+};
+
+class pwdgrp_check {
+  pwdgrp_state	state;
+  FILETIME	last_modified;
+  char		file_w32[MAX_PATH];
+
+public:
+  pwdgrp_check () : state (uninitialized) {}
+  operator pwdgrp_state ()
+    {
+      if (state != uninitialized && file_w32[0] && cygheap->etc_changed ())
+        {
+          HANDLE h;
+          WIN32_FIND_DATA data;
+
+          if ((h = FindFirstFile (file_w32, &data)) != INVALID_HANDLE_VALUE)
+            {
+              if (CompareFileTime (&data.ftLastWriteTime, &last_modified) > 0)
+                state = uninitialized;
+              FindClose (h);
+            }
+        }
+      return state;
+    }
+  void operator = (pwdgrp_state nstate)
+    {
+      state = nstate;
+    }
+  void set_last_modified (FILE *f)
+    {
+      if (!file_w32[0])
+        strcpy (file_w32, cygheap->fdtab[fileno (f)]->get_win32_name ());
+
+      BY_HANDLE_FILE_INFORMATION inf;
+      if (GetFileInformationByHandle (cygheap->fdtab[fileno (f)]->get_handle (),
+                                      &inf))
+        last_modified = inf.ftLastWriteTime;
+    }
+};