I've found some patches that may make you happy. It looks like the yytext_ptr error (if you don't specify -l) is the way it's supposed to work (didn't look into that a lot). All builds can be patched to use flex -l instead of just flex. If you don't want to do that there's a patch here: http://mirror.vtx.ch/lfs/patches/downloads/flex/flex-2.5.31-yytext_ptr-1.patch (untested by me)

There's another error though. It has to do with 'yy_more_offset' and 'yy_prev_more_offset'. A patch can be found here: http://sourceforge.net/tracker/index.php?func=detail&aid=720976&group_id=72099&atid=533379

I have tested this one and it fixed my tetex woes. It was submitted almost a year ago, but it looks like no one's looked at it.

The combination of those two (patch or -l and this second patch) should fix all of our flex woes.