v0.4.0-rc2

All major 0.4 changes are in, we continue with bugfixes and backports toward a final 0.4 release.

A prepared tarball (the output of make light-source-dist) is attached below in julia-0.4.0-rc1_fa52609644.tar.gz, use this if a source tarball is desired, as it contains a small amount of preparation that a simple archive of the git repository does not. For source builds in restricted environments (e.g. no network access) use the output of make full-source-dist attached below in julia-0.4.0-rc1_fa52609644-full.tar.gz as it already contains all dependencies pre-downloaded and ready for compilation.