DTrace: NFS translators should be split into client/server pieces

Belatedly update the provider with changes from OpenSolaris:

PSARC 2008/050 DTrace NFS v3 Provider
6696397 NFS v3 provider reports all UDP clients as 0.0.0.0
6711844 assert: vp->v_shrlocks

Obtained from:	Illumos
Print RDSEED, ADX, and SMAP.

Pointed out by:	kib
Add the most current CPUID7_* definitions.
Fix the value of NT_FREEBSD_TAG to be the same as ABI_NOTRTYPE in lib/csu.
Add NT_FREEBSD_NOINIT_TAG for the value of CRT_NOINIT_NOTETYPE.
Check for both of these when detecting a FreeBSD binary in gdb.
Revert revision 249323, the PR/177624 is confusing, that bug is caused
by using buggy getcontext/setcontext on same stack, while swapcontext
normally works on different stack, there is no such a problem.
When calculating the number of reserved nodes, discount the pages that will
be used to store the nodes.

Sponsored by:	EMC / Isilon Storage Division
Avoid copying memory if SIGCANCEL is not masked.
Remove debug code.
Move the previously added CPUID7 macros to CPUID_STDEXT.
Remove EOL whitespace.
Make siis(4) and mvs(4) send bus_get_dma_tag() requests to parent buses
passing real bus' child pointers instead of grandchilds.

Requested by:	kib
Both NFS clients can deadlock when using the "rdirplus" mount
option. This can occur when an nfsiod thread that already holds
a buffer lock attempts to acquire a vnode lock on an entry in
the directory (a LOR) when another thread holding the vnode lock
is waiting on an nfsiod thread. This patch avoids the deadlock by disabling
readahead for this case, so the nfsiod threads never do readdirplus.
Since readaheads for directories need the directory offset cookie
from the previous read, they cannot normally happen in parallel.
As such, testing by jhb@ and myself didn't find any performance
degredation when this patch is applied. If there is a case where
this results in a significant performance degradation, mounting
without the "rdirplus" option can be done to re-enable readahead
for directories.

Reported and tested by:	jhb
Reviewed by:	jhb
MFC after:	2 weeks