This is a malformed :option: tag -- we don't have an option directive that...

This is a malformed :option: tag -- we don't have an option directive that matches it, so turning it actual text instead of a markup tag. This will hopefully fix the clang docs build (http://lab.llvm.org:8011/builders/clang-sphinx-docs/builds/15194/steps/docs-clang-html/logs/stdio)

llvm-svn: 275407