Allow direct navigation to static analysis checker documentation through SARIF exports.

This adds anchors to all of the documented checks so that you can directly link to a check by a stable name. This is useful because the SARIF file format has a field for specifying a URI to documentation for a rule and some viewers, like CodeSonar, make use of this information. These links are then exposed through the SARIF exporter.

llvm-svn: 349812