[glibmm] (2 commits) Non-fast-forward update to branch wip/dboles/ustring

[Daniel Boles <dboles src gnome org>]

The branch 'wip/dboles/ustring' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  bf71775... ustring: Replace 9×compose() with 1 variadic template
  c31013d... ustring: Replace 8×format() with 1 variadic template

Commits added to the branch:

  8986d68... ustring: Replace 9×compose() with 1 variadic template
  75f5d2a... ustring: Replace 8×format() with 1 variadic template