Since a non-cygwin gmake trips up the github cygwin action, let's just
require that the user put a good "make" early on their path (a simple
`ln -s `which gmake` ~/bin/make` with the right $PATH works fine).
The release script & the patch management script now require the use of
an auto-build-save dir that makes it much easier to keep the generated
files from melding together, and remembers the configure setup for each
patch branch.
We now put the configure.sh, config.h.in, and aclocal.m4 files in the
alternate build dir along with the other generated files. This requires
that we create symlinks for configure.ac & m4 in the build dir, which is
handled on the first run of configure or prepare-source. I also changed
the patch-branch handling away from the .gen-stash dir to an automatic
build/$PATCH subdir idiom that will keep each branch's configuration
separated. These automatic build dirs are only used when there is a
.git dir, a build/master dir, and no top-dir Makefile. You'll also
want to have package/make early on your path for optimal ease of use.
