--enable-cgen-maint

[Ben Elliston]

I'm about to commit some changes that permit --enable-cgen-maint to be
passed into SID's collection of `configure' scripts.  When you do so,
you may activate sections of your cpu's Makefile.am using:

if CGEN_MAINT
  ..
endif

A likely scenario is to surround a set of dependency rules which
ensure that the generated files (ie. `foo-decode.cxx') are up to date
relative to your cgen description (ie. `foo.cpu'), rebuilding as
necessary.

The only other required change is to activate the AM_CONDITIONAL code
using a new macro for this very purpose.  Place something like this in
your cpu's configure.in:

  dnl enable automatic rebuilding of cgen-generated files
  RH_CGEN_MAINT

Please contact me if you have any questions/problems.

Ben