Misc: Drop support for older browsers; update support comments

That includes IE<8, Opera 12.x, Firefox<29, Safari<6.0 and some hacks
for old Blackberry.

Fixes gh-1836
Fixes gh-1701
Refs gh-1815
Refs gh-1820
BTW, we still have this code on `master`, it's in the function called `fixInput`. So either it's at least present in IE9 or we have unneeded code on `master`.