there's a buffer size problem that is very rarely hit by any normal
programs but appears when compiling some of the nuttier lunix code.

solution: if a line of code is longer than the default buffer size
(30k) then we realloc the buffer.

this isn't currently triggered by any plan9 code and will hopefully
never be.

for an example of what could happen in loonix-land see this gcc-parsed
code:

http://pages.cpsc.ucalgary.ca/~mirtchov/screenshots/ffmpeg.gif

andrey