updating the build

[William Pursell]

I've been working on updating the configury for screen, and have
gotten to a state that could reasonably be merged.  (Also, I don't
know that I'll have much time to look at this over the next few
months.)  Primary benefits:

Uses gnulib's getloadavg, so the configury for that function is
up-to-date and actively maintained.

Uses config.guess to determine host and arch.  Again, the primary
benefit being active maintenance of the checks.

Everything can be specified at configure time.  For example,
to set USRLIMIT, the user can either do it the old way
and edit config.h after running configure, or run configure
with the argument "usrlimit=20".  I pick usrlimit as an
example because both my fork and the current master
do not compile with usrlimit set, so that leads to...

I've succesfully built with default settings on OSX/i386,
freeBSD 6.3/i386 and netBSD/sparc64.  These are all BSD
leaning, so I would appreciate feedback from anyone on
the build on other platforms.    The git repository is at:
address@hidden:wrp/wscreen.git in branch wrp.  To build,
one must have gnulib installed with gnulib-tool in the
PATH, and autoconf 2.63.251.  Or, grab the tarball
from http://www.wpursell.net/screen and the autoconf
and gnulib dependencies are removed.

This fork provides no new functionality, but is a good
step towards bringing screen up to date.

Micah, Juergen, et al., please let me know if there
is anything objectionable that causes you to refrain
from merging.

-- 
William Pursell