revlog: merge hash checking subfunctions This patch factors the behavior of both methods into 'checkhash'.

bookmarks: make bookmarks.comparebookmarks accept binary nodes (API) Binary bookmark format should be used internally. It doesn't make sense to have optional parameters `srchex` and `dsthex`. This patch removes them. It will also be useful for `bookmarks` bundle2 part because unnecessary conversions between hex and bin nodes will be avoided.