Mostly curtail font-lock-mode

[Vasilii Kolobkov]

I had font-lock-mode disabled for most of the major modes (sans
whitelist in font-lock-global-modes), but ran into a problem.

rcirc-track-minor-mode highlights some notification in its mode line
display by setting a `font-lock-face' text property.  And it seem to
have no effect if the font-lock mode is disabled.

Now i wonder what would be the most effective way to disable most of the
work font-lock would do (e.g. figuring out the syntax structures), but
still have it nominally enabled so that i could make use of it in the
mode line?  Any hints on general direction to do it would be very much
appreciated!