(bug 36855) escape literal % in tex input
(bug 36855) escape literal % in tex input

This removes support for MathML % comments, just as with texvc

PS2: Fix for regex lookbehind issue

Change-Id: I0cb026d749733ed3dbba8faacb163be4438fc6bb

kwangkim/mathoid,MonashAlexandria/mathoid,kwangkim/mathoid,wikimedia/mathoid,wikimedia/mathoid,physikerwelt/mathoid-server,kwangkim/mathoid,kwangkim/mathoid,physikerwelt/mathoid-server,physikerwelt/mathoid-server,MonashAlexandria/mathoid,wikimedia/mathoid,wikimedia/mathoid