gmmproc m4 changes

[Murray Cumming <murrayc murrayc com>]

I have removed some convert_*.m4 files from glibmm because they don't
belong there and were duplicated in gtkmm, causing confusion.

Some modules will now need to add a line in their configure.ac so they
can use the extra conversions from gtkmm. For instance, with
gtksourceviewmm:

MM_PKG_CONFIG_SUBST([GMMPROC_EXTRA_M4_DIR], [--variable=gmmprocm4dir
gtkmm-3.0])

You can see that change here:
http://git.gnome.org/browse/gtksourceviewmm/commit/?id=9b7a097649b7109e079f84aa6a60a618008fce27


Note that this requires the latest mm-common and gtkmm from git master.
Adding that line will be harmless if using an older version of gtkmm
that doesn't have that variable, and an older glibmm/gmmproc that
doesn't need it.

This uses a new .pc variable that I added to gtkmm:
http://git.gnome.org/browse/gtkmm/commit/?id=60ae86ecd8c848ae0ed58985edfd7f92367fb29f
We might need to add this to other modules too, but time will tell.

-- 
murrayc murrayc com
www.murrayc.com
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