Mercurial: Use TextEditor::SyntaxHighlighter

Change-Id: Ic215b778a6365d8bce5cb8eeb0d016d8ce80e476
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Mercurial: Fix highlighting

* Hash is not a comment, "HG:" is.
* First line *that is not a comment* is a summary

Change-Id: If4e3428bfd4461dc105583a998be5d8185be3ab6
Reviewed-by: Christian Stenger <christian.stenger@digia.com>