Document PR_PSERIALIZE. Remove documentation for pool_cache_setpredestruct().

Add pool_cache_setpredestruct(), which allows a pool cache to specify
a function to be called before the destructor for a batch of one or more
objects is called. This can be used as a synchronization point by
subsystems that rely on the type-stable nature of pool cache objects or
subsystems that use other forms of passive serialization.

Remove superfluous whitespace & macros.

slightly change and fix the semantics of pool_set*wat(), pool_sethardlimit()
and pool_prime() (and their pool_cache_* counterparts):

- the pool_set*wat() APIs are supposed to specify thresholds for the count of
free items in the pool before pool pages are automatically allocated or freed
during pool_get() / pool_put(), whereas pool_sethardlimit() and pool_prime()
are supposed to specify minimum and maximum numbers of total items
in the pool (both free and allocated). these were somewhat conflated
in the existing code, so separate them as they were intended.

- change pool_prime() to take an absolute number of items to preallocate
rather than an increment over whatever was done before, and wait for
any memory allocations to succeed. since pool_prime() can no longer fail
after this, change its return value to void and adjust all callers.

- pool_setlowat() is documented as not immediately attempting to allocate
any memory, but it was changed some time ago to immediately try to allocate
up to the lowat level, so just fix the manpage to describe the current
behaviour.

- add a pool_cache_prime() to complete the API set.

Remove copy-paste garbage.

branches: 1.19.2; 1.19.34;
Document pool_cache_sethardlimit(9), the faithful friend of
pool_sethardlimit(9).

branches: 1.18.2;
Describe the arguments to ctor and dtor.

branches: 1.17.4;
Remove boilerplate in CODE REFERENCES on file paths.
Describe in intro(9) how to read paths in the CODE REFERENCES section.

Whitespace fix.

Cross-link a little.

Fix argument names in description of pool_cache_init().

- pool_cache_invalidate(): broadcast a cross-call to drain the per-CPU
caches before draining the global cache.
- pool_cache_invalidate_local(): remove.

Bump date for new pool_cache_invalidate_local().

Add pool_cache_invalidate_local() to the pool_cache(9) API, to permit
per-CPU objects invalidation when cached in the pool cache.

See http://mail-index.netbsd.org/tech-kern/2009/10/05/msg006206.html .

Reviewed by bouyer@. Thanks!

Fix typo.

Remove trailing whitespace, and fix a typo.

Mention kmem(9).

Convert TNF licenses to new 2 clause variant

branches: 1.6.4; 1.6.6;
Sync with reality. This is a work in progress.

branches: 1.5.4;
- Add link to memoryallocators(9) in kmem_*(9), vmem(9), uvm(9), malloc(9),
pool(9) and pool_cache(9) manuals.
- Sort uvm(9) "SEE ALSO" section.

Fix a tyop.

s/NetBSD.ORG/NetBSD.org/
s/netbsd.org/NetBSD.org/

OK'd by martin@

Fix a Xr (missing section), and sort SEE ALSO.

a pool_cache(9) manpage.
maybe incomplete, but better than none.