add note to INSTALL file about gcc 4.9.0 not being supported
update version reference in the README file
add tarball-producing targets to Makefile for ease of release

my old, out-of-tree release script that performed a clone rather than
using git archive checked the VERSION file to make sure that it
matched before doing a release. I believe there should be a way to do
the same with git commands (without resorting to checking out the
desired tag) but I have not yet found a way, so care should be taken
when using these targets that the correctness of the VERSION file is
not overlooked.
release 1.1.3