* develop: (85 commits)
Make libxcb compile with gcc 4.9.
disable parallel install for glib (found races)
disable cairo-trace, which is incompatible with older libiberty.h.
Fix LaunchMon on newer gcc versions.
Simplify output redirection in spack.util.executable
Allow completely empty config files.
Update cmake package to use http in all URLs.
Fix create, diy, edit, and repo commands to use multiple repos.
Add namespace option to find command.
Temporary fix: Clang is the default compiler on Mac OS X.
Netcdf requires cmake >=2.8.12
Mbedtls depends on cmake
Update libtool to 2.4.6
Update Julia to 0.4.3
Make binutils build on OS X
Add verbs and psm variants
py-matplotlib: depend on freetype
py-numpy: make blas/lapack optional dependencies
qhull: apply patch to work with libc++'s standard library
New package GNU tar
...
Package repositories now look like this:
top-level-dir/
repo.yaml
packages/
libelf/
package.py
mpich/
package.py
...
This leaves room at the top level for additional metadata, source,
per-repo configs, indexes, etc., and it makes it easy to see that
something is a spack repo (just look for repo.yaml and packages).
