(split) sh: Add -h option to SYNOPSIS

Reviewed by:	jilles
MFC after:	soon
(split) - Temporary fix for race in RUN driver which can
cause freed memory to be accessed.
- Properly lock callout_reset()'s.

MFC after:	1 week
(split) Fix a logic error when enabling MAC.
(split) Similar to r246614, fix panic on removing urtwn(4).  It happens because
nodes are freed after the adapter is gone.
(split) Reset the bit of the R92C_MCUFWDL associated with checksum report
before loading firmware page.  It may fix this problem:
"urtwn0: timeout waiting for checksum report"
(split) Merge branch 'CURRENT' (commit 'f19bbde6')