Increase the number of TLB entries expected by the kernel debugger
on CHERI.
Flush stdout and stderr before forking children processes in cheritest:
otherwise, problems can be encountered with buffered output if something
other than a tty is used for output -- e.g., a pipe in the event you
pipe the output of cheritest through grep.
When dealing with shadowed objects undergoing a copy-on-write fault, be sure
to use the final resolved object's tag flags rather than the first one's as
the origin of flags to pmap_enter() controlling use of tags.

Add a comment to another point in the VM code, when a page is moved between
objects rather than copied, and it's not clear that the pmap will receive a
notification to update the TLB's flags.
Add a commented out version of the changes to the MIPS pmap to process
tag-related flags to pmap_enter() so that it's checked in somewhere.
Currently, using this code encounters problems because the flags appear
improperly for certain pages originating in the default pager.
For the CHERI_SET_STACK sysarch(), ensure that we check the user-provided
stack structure not just for a stack pointer that is in range, but also a
permitted alignment.

Spotted by:	MIT/LL
Print out additional capability register state when taking a CP2 exception;
now that we use a compiler, our register footprint is much later.
Trim two more bits from the PFN mask in EntryLo as we now occupy two more
for hardware at the top end, so have shifted the software-defined bits
further down.