quick and dirty fix for libhtml suicide.

example of the problem:

hget 'http://groups.google.com/group/comp.os.plan9/browse_thread/thread/69681ebd49278c67/3d01204ba294b513?lnk=gst&q=restricted+remote+address&rnum=1#3d01204ba294b513' | htmlfmt

the token arrays are reallocated on demand, however
more than one token can be lex'ed each time
round the loop. My fix just ensure there is plenty
of free space in the token array.

-Steve