[libcxx] Add new Sphinx documentation
This patch adds Sphinx based documentation to libc++. The goal is to make it easier to write documentation for libc++ since writing new documentation in HTML is cumbersome. This patch rewrites the main page for libc++ along with the instructions for using, building and testing libc++.
The built documentation can be found and reviewed here: http://efcs.ca/libcxx-docs
In order to build the sphinx documentation you need to specify the cmake options -DLLVM_ENABLE_SPHINX=ON -DLIBCXX_INCLUDE_DOCS=ON. This will add the makefile rule docs-libcxx-html.
Reviewers: chandlerc, mclow.lists, danalbert, jroelofs
Subscribers: silvas, cfe-commits
Differential Revision: http://reviews.llvm.org/D12129