Major build system changes landing

[Russ Allbery]

I'm landing major build system changes; expect the tree to be unstable
until I've finished committing.  This is the first pass through switching
the simple scripts from configure over to fixscript, as well as a rewrite
of Makefile.global and some general makefile cleanups.  Tested with both
GNU make and Solaris make, and I tried to use a strict subset of the make
stuff that we were already using.

-- 
Russ Allbery (rra at stanford.edu)         <URL:http://www.eyrie.org/~eagle/>