If the boss is unknown, we exclude the log - that is how
BossFilter::filter operates, and it is probably what the user wants if
they specify a -boss filter. However, in filter_early, the default for
unknown bosses was to return Inclusion::Include, which is not consistent
with filter. That lead to some logs being included, parsed and then
thrown away again.

This change makes the behaviour for unknown bosses between filter_early
and filter consistent, and therefore speeds up the search if -boss is
used.

Everybody calls bosses by different names (Soulless Horror vs Desmina,
Super Kodan Brothers, ...), so it might be good to have a list ready in
the help message.

Other names can still be used, but those are the end-user documented
ones now.

With evtclib 0.2, every boss has at least one name without space, so
every boss can be used. Still, for completeness's and consistency's
sake, we want to allow users to also specify boss names with spaces in
them. For example, if we print "Qadim the Peerless" as the name of the
boss, we might expect
    raidgrep -- -boss "Qadim the Peerless"
to work (instead of -boss qadimp). Therefore, we now allow boss names to
be quoted, so that we can properly persist the whitespace.

This does increase the build times, but it makes sure the binaries are a
bit smaller (especially a gain for the Windows binary). In addition, it
removes librt, which is unneeded and gave warnings in namcap.