Update to 1.8.1:

This release backs out a behavior change for so-called 'fast-forward'
merges on named branches.

    * annotate: rewrite to deal with crossed linkrevs (issue2682)
    * bookmark: fix invalidation of localrepo._bookmarkcurrent
    * cacert: improve error report when web.cacert file does not exist
    * contrib: update tcsh_completion for Mercurial 1.8
    * hgcia: accept "queued." xmlrpc return as success
    * hgweb: fix filelog rss links generation
    * hgweb: use tip in gitweb/monoblue filelog rss links (issue2677)
    * merge: back out single-parent fast-forward merge
    * merge: drop resolve state for mergers with identical contents (issue2680)
    * merge: improve unresolved conflicts warning (issue2681)
    * mergetools: add alternate registry keys for 32bit apps on 64bit O/S
    * mq: forbid commit of merge involving mq patches
    * subrepo: backout 67fbe566eff1, --force requires svn >= 1.5
    * subrepo: don't crash when git repo is missing
    * subrepo: handle svn tracked/unknown directory collisions
    * wix: drop bin/ folder from MSI installers (issue2673)

(wiz)