Major changes to mh_math, mh_masic and the agopt_ex package.

All packages now use etoolbox's toggles now instead of the plain \newif
structure.
Polyglossia is now also used for LuaTeX since TexLive 2013 contains a
sufficiently recent polyglossia version.
The new [math] option for mh_basic loads mh_math; it's pure convenience.