MFC r239185, r239196:

MFC r239185, r239196:
Some minor tunings/cleanups inspired by bde@ after previous commits:
 - remove extra dynamic variable initializations;
 - restore (4BSD) and implement (ULE) hogticks variable setting;
 - make sched_rr_interval() more tolerant to options;
 - restore (4BSD) and implement (ULE) kern.sched.quantum sysctl, a more
user-friendly wrapper for sched_slice;
 - tune some sysctl descriptions;
 - make some style fixes.

git-svn-id: svn://svn.freebsd.org/base/stable/9@241249 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f