* libmisc/pwdcheck.c: Do not include <pwd.h>. Include <shadow.h>

and "pwauth.h" only when compiled without PAM support.
* src/chfn.c, src/chsh.c: Do not include <shadow.h>
* lib/commonio.c: Do not include <shadow.h>. Do not include
  <pwd.h>. Include "nscd.h" instead of <nscd.h>.
* configure.in: Do not check if shadow.h exist, but make sure it
  exists.
* libmisc/pwdcheck.c, src/chfn.c, src/chsh.c, lib/defines.h,
  lib/shadowmem.c, lib/shadowio.c, lib/commonio.c:
  HAVE_SHADOW_H is no more needed (shadow.h should always exist).

src/chfn.c

@@ -36,9 +36,6 @@
 #include <signal.h>
 #include <stdio.h>
 #include <sys/types.h>
-#ifdef HAVE_SHADOW_H
-#include <shadow.h>
-#endif
 #ifdef WITH_SELINUX
 #include <selinux/selinux.h>
 #include <selinux/av_permissions.h>

src/chsh.c

@@ -41,9 +41,6 @@
 #include <selinux/selinux.h>
 #include <selinux/av_permissions.h>
 #endif
-#ifdef HAVE_SHADOW_H
-#include <shadow.h>
-#endif
 #include "defines.h"
 #include "exitcodes.h"
 #include "getdef.h"