First pass over Reid's document.

Changed the order of operations so that more of the fine tuning is
performed in the release branch.  This should free up mainline sooner to
resume development.
Removed information on the special release Makefile targets as I've never
used them for a release; Tanya is investigating their integration, and they
can be re-added if she uses them.
Added an outline for building the LLVM GCC binary distributions.  I will
be filling that section out later (but before the 1.7 release).

llvm-svn: 27595