MEDIUM: evports: permit to report multiple events at once

MEDIUM: evports: permit to report multiple events at once

Since the beginning in 2.0 the nevlist parameter was set to 1 before
calling port_getn(), which means that a single FD event will be reported
per polling loop. This is extremely inefficient, and all the code was
designed to use global.tune.maxpollevents. It looks like it's a leftover
of a temporary debugging change. No apparent issues were found by setting
it to a higher value, so better do that.

That code is not much used nowadays with Solaris disappearing from the
landscape, so even if this definitely was a bug, it's preferable not to
backport that fix as it could uncover other subtle bugs that were never
raised yet.