Do not generate gh-pages for branches starting with "ycm-"

These branches will be used for stable branches (i.e. ycm-0.1) and we
already have documentation for tags.
Update docs/cmake.py from CMake master

(last commit 15a8af21e8bd8354dfff2063e01f695f85efdeb8)

Keep patch to make intersphinx links work.
Fix man and qch documentation generation