[PATCH] Docs for llvm-symbolizer tool

[Dmitri Gribenko]

  To compile HTML files, do:

  ```cd llvm/docs
  make -f Makefile.sphinx```

  HTML files are put into `llvm/docs/_build`.

http://llvm-reviews.chandlerc.com/D462

BRANCH
  svn

ARCANIST PROJECT
  llvm