Replace the build process. The new one requires GNU Make, Autoconf

Replace the build process.  The new one requires GNU Make, Autoconf
and Autoconf macros that come with Automake.  It supports multiple
separate builds of the same source tree, and updates dependencies
automatically.  Targets info, html, install, install-html, uninstall
and dist are not yet implemented.

System configuration is now automatic.  Previously, you had to choose
one of several canned system configurations, defined in Make.sysdefs.
Currently, system configuration always uses UCONTEXT for LWP, and
chooses LWP only if its requirements are met.

Feature configuration changed: instead of editing build.conf (further
processed by doconfig), you pass arguments to configure.  Note that
build.conf settings that can be overridden in econfig have no
configure equivalent; just edit econfig instead.

Because generated headers complicate makefiles, fold gamesdef.h into
its users: path.c and ipglob.c become path.c.in and ipglob.c.in,
constants.c, vers.c, options.h simply hardcode defaults (most of them
are run-time configurable).

Call the client empire instead of emp_client.  This matches what the
old standalone build did.