Log Message:
x11/drawterm: update to latest snapshot.

Further simplify Makefile and avoid to override pkgsrc defaults wherever
possible. Use PTHREAD_AUTO_VARS to handle pthread flags instead of
relying on package self-defined os-dependent choices.

Sync package with most recent upstream commit (20230224).
This pulls some noteworthy changes and fixes:

* libmemdraw: update draw.c from 9front
* make USED() macro cast to void, so it works with non-scalars.
* devcons: cleanup kbdputc().
* keyboard.h: update from 9front.
* libauthsrv: better passtodeskey().
* clear parentesis warning from GCC in libc, devdraw, libsec, libip.
* libsec: fix inconsistent prototypes for des.
* devfs: create handle OEXCL, mask permissions with parent directory,
  fix leaks.
* Remove unused Screeninfo screen struct.
* x11: Fix colormap allocation.