Merge updated git-gui and gitk that call each other

Merge git://repo.or.cz/git-gui and git://git.kernel.org/pub/scm/gitk/gitk

    * git://repo.or.cz/git-gui:
      git-gui: Show special diffs for complex conflict cases.
      git-gui: Make F5 reselect a diff, if an untracked file is selected.
      git-gui: Reimplement and enhance auto-selection of diffs.
      git-gui: Support conflict states _U & UT.
      git-gui: Support more merge tools.
      git-gui: Don't allow staging files with conflicts.
      git-gui: Support calling merge tools.
      git-gui: Support resolving conflicts via the diff context menu.
      git-gui: Mark forgotten strings for translation.
      git-gui: Allow specifying an initial line for git gui blame.
      git-gui: Better positioning in Blame Parent Commit
      git-gui: Support passing blame to a parent commit.
      git-gui: Support starting gitk from Gui Blame
      git-gui: Teach git gui about file type changes

    * git://git.kernel.org/pub/scm/gitk/gitk:
      gitk: Add menu item for calling git gui blame
      gitk: Add option to specify the default commit on command line