Remove unused variable; no binary change.

From Michael W. Bombardieri, thanks!

combine malloc/memset into calloc. from Michael W. Bombardieri

Nuke more unused variables.

ok millert@

it is not necessary to cast the result of malloc/calloc.
also replace some 0s with the modern concept of NULL

flex_alloc and flex_free are nothing more than malloc and free, so replace
them with the real functions so as to not trick people into thinking they
are special

orbital strike from moonbase knf

repair some of the preposterously damaged indentation

we don't keep vim modelines in files

Update flex from ancient 2.5.4 to the recent 2.5.39.
This work was all done by Serguey Parkhomovsky. Thanks.
Some changes from upstream:
* Removed autotools cruft/localization/texinfo manual/etc
* Kept the old manpage, as the new manpage is content-free
* Used safe string handling functions and fixed several compiler warnings
* pledge(2). Flex 2.5.39 now forks/execs its filter chains and needs proc
exec in addition to what was previously pledged
* Removed register keyword from all variable declarations
* renamed parse.c, parse.h, scan.c, skel.c with init prefix so compiling
flex outside of obj by accident wouldn't clobber the bootstrap files
* Minor fixes (spelling, accessing buf[strlen(buf) - 1] for zero-length
strings in initscan.c/scan.l, etc) that were already in our tree

This is a huge change, so it's going in the tree code bomb style.
I'm not excited about the growth in complexity (like now running m4
to _post_ process lexers) but hopefully this will be a one time update
and we will now take "ownership" of the code.