MFC r250147:

procstat_getpathname: for kvm method, instead of returning the error
that the method is not supported, return an empty string.

This looks more handy for callers like procstat(1), which will not
abort after the failed call and still output some useful information.
r250503

Get rid of libl dependency.  We needed it only to provide yywrap.  But
yywrap is not necessary when parsing a single hast.conf file.

Suggested by:	kib
Reviewed by:	pjd
MFC r250379, r250503:

HAST module for bsnmpd(1).

Reviewed by:	harti, pjd
MFC r250380:

Register OID for HAST module.
MFC r250405:

Move snmp_hast manual to section 3, where all other manual pages for
bsnmp modules are located.

Section 3 (Library Functions) looks wrong for this manual page, which
contains only module description, that is why initially it was located
to section 8 (System Manager's Manual).  On the other hand manual
pages for all other bsnmpd modules are already located in the section
3, and having all pages in one section looks more consistent.  Also,
currently, similarly to manuals for other modules, snmp_hast manual
contains LIBRARY section, which is not good style for section 8.