setup: explain to distutils how we write rc versions
When we use a rc version number (e.g. 4.8rc0), bdist_msi is using
distutils.StrictVersion to parse it into a tuple of numbers.
By default, StrictVersion.version_re only recognizes [ab] for alpha/beta,
where mercurial may use '-rc' or 'rc'.
This change makes StrictVersion parse correctly our version numbers, so that
bdist_msi doesn't fail on rc versions.
#if no-windows no-osx
$ mkdir -p xdgconf/hg
$ echo '[ui]' > xdgconf/hg/hgrc
$ echo 'username = foobar' >> xdgconf/hg/hgrc
$ XDG_CONFIG_HOME="`pwd`/xdgconf" ; export XDG_CONFIG_HOME
$ unset HGRCPATH
$ hg config ui.username 2>/dev/null
foobar
#endif