hgweb: show instabilities of a commit
In paper, coal, gitweb and monoblue a new "tag" (or multiple, if there are many
instabilities) is added to the same line that has phase, branch, etc of a
changeset; in gitweb and monoblue this element has a light red background, in
paper and coal the element is black and underlined. In spartan theme
instabilities are shown on a separate line.
While test-obsolete.t uses first(phasedivergent()) revset to pick a changeset
to test, that particular changeset is also an orphan, so two different
instability tags are displayed.
ERROR: FIXME: This is a known failure of filelog.size for data starting with \1\n
OK.