Tuxmath has a top-level directory called linebreak/ that contains code copied from the GNU gettext library, which is used for wrapping of display text (currently just in credits.c).

For this task, this code needs to be moved into our t4k_common library, and the build systems (both Automake and Cmake) adjusted accordingly on both ends.

Also, we have our own wrapper code in src/linewrap.c that should be copied into t4k_common as src/t4k_linewrap.c, following the naming convention for t4k_common.

The third-party code in linebreak/ should not be renamed or edited.  The tux4kids-written functions in linebreak.c should be renamed with the T4K_* prefix and commented so as to support Doxygen.

To be sure that the above code works, adjust tuxmath to use the new functions from t4k_common rather than the ones currently in use.

After the above is done, supply two patches, one for t4k_common (which will be applied and committed, if done well), and one for tuxmath (for testing).