[PATCH] Added doxygen support for the tools of clang-tools-extra repo

[Ariel Bernal]

  yes this files are the same as the ones in clang/docs but with minor modifications,

  doxygen.intro : modified the description to match the tools in clan-tools-extra.
  doxygen.footer: no modification
  doxygen.css: no modification
  doxygen.cfg.in: added input files from cpp11-migrate (this one for now, we can add the other tools later)
  doxygen.header: modified the description
  Makefile: copied from clang/docs with minor modifications.

http://llvm-reviews.chandlerc.com/D451