In ccgDM and emDM, looptri array recalculation was being handled
directly by `*DM_getLoopTriArray` (`getLoopTriArray` callback), while
`*DM_recalcLoopTri` (`recalcLoopTri` callback) was doing nothing.
This results in the array not being recalculated when other functions
that depend on the array data called the recalc function.
This moves all the recalculation code to `*DM_recalcLoopTri` and makes
`*DM_getLoopTriArray` call that.
This commit also makes a minor change to the `getNumLoopTri` function,
so that it returns the correct number without having to recalculate the
looptri array.
Reviewed By: mont29
Differential Revision: https://developer.blender.org/D2375
7fe7835d13