Simplify stdout buffering

* src/sysdep.c (_sobuf): Remove; we no longer need this
microoptimization.
(init_sys_modes): Simplify by assuming setvbuf.
1 job for master in 51 minutes and 13 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #2303
test-all

00:51:13

 
Name Stage Failure
failed
test-all Test
Makefile:318: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:293: recipe for target 'check-expensive' failed
make[1]: Leaving directory '/builds/emacs/emacs/test'
make[1]: *** [check-expensive] Error 2
Makefile:957: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1