* stepmake/bin/install-sh: Include latest from libtool.

* stepmake/bin/install-sh: Include latest from libtool.

* stepmake/configure:
* configure: Regenerate.

* config.make.in: Remove dead variables.  Add OPTIONAL/REQUIRED lists.
(USER_CFLAGS): Bugfix, include CPPFLAGS.

* configure.in: Use new OPTIONAL/REQUIRED mechanism.

* stepmake/aclocal.m4: Add mechanism for checking OPTIONAL or
REQUIRED programs and version.  Try to continue configuring, list
missing programs at the end, but don't generate a GNUmakefile if
REQUIRED programs are missing.  Cleanups, junk obsolete stuff.
Fix Cygwin detection, drop '32' suffix.  Hoping this is not too
fancy for some older systems.

* config.make.in USER_CFLAGS: Include CPPFLAGS too.