missing description of pool_destroy(). Fix some minor nits.
It isn't clear from the source whether pool_reclaim() and pool_drain()
should belong to the exported API. At least it seems they aren't used.
No descriptions for these functions exist in this manpage.
allocations should fail if the pool is at its hard limit.
Document flag in pool(9).
Use it in mbuf.h for the first allocate call for M_GET, M_GETHDR, and
MCLGET, so that m_reclaim gets called even for blocking allocations.
Also, while here, expand apparently incorrectly .Dd month abbreviations.
(I thought about doing this in tmac/doc-common...heh...that would have
allowed a possible reverse map back to abbreviations.)
gmcgarry