(bug 35188) Do not poison the tex formula with markup

We move the block/inline styling (aka display vs textstyle) markup into
a filter used just before rendering. This way the 'used' formula will
not suddenly contain styling information that wasn't part of the
original formula.

Change-Id: Ie0c308c31d38581e556dc73109879c7a3d365121
Merge "(bug 35188) Do not poison the tex formula with markup"