Style cleanups.  No intended functional changes.

 o Group functions by by their functionality.
 o Remove superfluous declarations.
 o Remove more unused (#ifdef'd out) code.

Sponsored by:	Spectra Logic Corporation
Style changes.  No intended functional changes.

 o rename flush_requests => xbd_flush_requests
 o rename xbd_setup_ring => xbd_alloc_ring

Sponsored by:	Spectra Logic Corporation
MFC after:	1 week
test: Remove -ntXY and -otXY primaries.

This reverts commit r247274.

As maintainer of sh, I disapprove of this feature addition.

It is too specific and can be done without easily using find(1) or stat(1).
I will add some hints to the test(1) man page shortly.

In general, FreeBSD sh is not the place to invent new shell language
features. This is how it has been maintained and adding features randomly
does not work with that.

The new syntax (e.g. [ FILE1 -ntca FILE2 ]) looks cryptic to me.
test(1): List non-standard primaries.
MFV: Redo the fixup using the submitted version accepted by upstream.
test(1): Add information about replacing -nt/-ot.