+ improve description of limits for color values and color pairs in
curs_color.3x (prompted by patch by Tim van der Molen).
+ add VERSION file, using first field in that to record the ABI version
used for configure --with-libtool --disable-libtool-version
+ add configure options for applying the ".map" and ".sym" files to
the ncurses, form, menu and panel libraries.
+ add ".map" and ".sym" files to show exported symbols, e.g., for
symbol-versioning.
