Merge branches 'doc.2019.01.08a', 'fixes.2019.01.08a', 'sil.2019.01.10a', 'srcu.2019.01.08a' and 'torture.2019.01.08a' into HEAD

doc.2019.01.08a:  Documentation updates.
fixes.2019.01.08a:  Miscellaneous fixes.
sil.2019.01.10a:  Removal of a few more spin_is_locked() instances.
srcu.2019.01.08a:  SRCU updates.
torture.2019.01.08a: Torture-test updates.

HEAD contains the following, due to a minor merge conflict:

consolidate.2019.01.10a:  RCU flavor-consolidation cleanups.
fwd.2019.01.08a:  Grace-period forward-progress updates.