Version 2: Fix bug: Makefile doesn't detect some out-of-date libraries.

Version 2: Fix bug: Makefile doesn't detect some out-of-date libraries.
 The previous fix (SVN 28504) didn't quite work since
 nmake always errored out if the libraries were not up-to-date; this
 prevented doing an nmake ... setup.

 This version of the fix:
 1. Gets the library status (checktag) at the beginning of the make.
 2. Effectively does the actual testing of the status whenever
    a target with $(LIBS_CHECK) as a dependency is invoked.

 Result: nmake ... [all] will error-out while nmake .... setup will
  work properly.

 Note that nmake ... setup will now show an initial error message
  (from checktag) if the libraries are out of date; setup will still
  proceed normally.
  This is a slight change from the current behavior wherein no
  error message occurs when nmake ... setup is invoked when the
  libraries are out of date.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@28516 f5534014-38df-0310-8fa8-9805f1628bb7