bookmarks: write bookmarks file deterministically
Bookmarks are internally stored as an unsorted dictionary. Let's at
least write out the bookmarks file in a deterministic order so it is
easier to test, diff, etc.
Differential Revision: https://phab.mercurial-scm.org/D2469
#require docutils gettext
$ $TESTDIR/check-gendoc de
checking for parse errors
Die Dateien werden dem Projektarchiv beim n\xc3\xa4chsten \xc3\x9cbernehmen (commit) hinzugef\xc3\xbcgt. Um dies vorher r\xc3\xbcckg\xc3\xa4ngig zu machen, siehe:hg:`forget`. (esc)
warning: please have a space before :hg: