We have a configure.ac check for lib.exe that attempts to enable
creation of .lib files for our 5 public libraries.  That has been broken
for a long time for two reasons:

 1) the Makefiles hardcode 'lib' instead of 'lib.exe'

 2) we dropped generation of .def files quite some time ago (except for
    in gthread where we have the two-symbol file under version control)

Add new rules for creating .def files from dumpbin.exe (which you should
have if you have lib.exe) and fix the .lib rules to use lib.exe.

Add a bit of $(AM_V_GEN) all around, as well.