[PATCH v2 0/6] introduce common.m4

[Tom Tromey <tromey@redhat.com>]

This series is an updated version of my earlier patch to add a
"common.m4":

    https://sourceware.org/ml/gdb-patches/2013-04/msg00739.html

The idea behind common.m4 is to have all configury needed by common in
a single place.  This avoids having to add parallel checks by hand to
both gdb and gdbserver's configure scripts.

I believe this version addresses Pedro's comments.  Now the
"redundant" checks are not removed; instead, each configure script
checks for what it needs.

Eventually I think it makes sense to move gnulib, the common bits, and
gdbserver to be top-level subdirectories in src.  This was difficult
before, due to CVS modules; but now it is much simpler to do, and I
think has benefits in terms of clarity and modularity.  When this is
done, common.m4 will continue to exist, at least in the short term, so
that macros used by its headers are still properly defined by its
users.

Tom