Main changes:
* MD5 is stored in binary in database now, so MySQL has easier life
* Everything produced by renderMath is protected from further evaluation
Mechanism for doing that is ugly as hell (it's almost the same as one used
by <nowiki>)
* texvc is compiled to native code by default now. It probably won't make much
difference in terms of speed, as it's latex dvips and convert who take
most resources, but its free gaim, so why not use it (well, we could
also consider stripping texvc binary to make it a bit smaller, or doing some
really obscure optimalizations, but texvc is really not a performance
bottleneck).
Open questions:
* How to put TeX in safe mode ?
* Did you really measure that dir/a/ab/abcdef012345678.png is significantly
faster than dir/abcdef012345678.png and I should make math mode use this
trick too or you were just guessing and I can ignore that ?