Add function and wrapper to switch lockmgr and vnode lock back to
auto-promotion of shared to exclusive.

Approved by:	re (gjb)
MFC r270797:
Direct access to the quota files, in particular, lookup, causes lock
conflict with the quota metadata access. Mark quota vnode lock as
recursive and always exclusive to avoid the problem.

Approved by:	re (gjb)
MFC r261095,r263464,r263752,r264189

r263464,r263752,r275189:

Mask out SRR1 bits that aren't exported to the MSR.

This appears to fix a strange condition with X on 32-bit PowerBooks I
observed, caused by one of these bits getting set in the mcontext, but
not set in the thread, which is a symptom of another problem, more
difficult to diagnose.  Since these bits aren't exported anyway, this
change makes it more explicit that the bits aren't MSR-related in SRR1.

r261095:

Fix 32-bit signal handling on ppc64.  This was broken when the
PSL_USERSTATIC macro was changed.  Since copying 64-bit srr1 into
32-bit srr1 drops the upper 32 bits, any bits set in the context were
dropped, meaning the context check fails.  Since 32-bit set_context()
can't change those bits anyway, copy the ones from the current context
(td->td_frame) before calling set_context().

Approved by:	re
Relnotes:	yes (Affects 10-stable, but not 10.0-release)
MFC 270222:
Bump the default size of cpuset_t masks in userland from 128 bits to 256.

This should not be an ABI change since the various public APIs that use
cpusets all include an explicit size parameter in addition to the cpuset
parameter.

Approved by:	re (gjb)