Includes an update to the guile m4 package, and tweaks the build so that both 2.2 and 3.0 should work fine.
Grab some newer version of the autotools m4 archive, as we need those to setup code-coverage. Remove some unneeded ones.
Use an update guile.m4; it seems different systems (Fedora, arch, gentoo, ...) have guile installed under different names. Try to handle all of those. For this, we include the upstream guile.m4 and add support for guile-snarf.
