Created SoftSnow XChat Filter 1.2.2

Created SoftSnow XChat Filter 1.2.2

Cleanup: use /usr/bin/perl in shebang (#!) line, put script version in
variable, just like script name.

Add /FILTER command, with ON, OFF, STATUS, HELP, SERVER, ALL
subcommands.  Those allow turning filter on and off, limiting
filtering to current IRC server or filtering all output, checking
status of filter (if it is turned on, if it is limited to single
server), and getting help.  Filter is now turned OFF by default.

NOTE: '/filter help' had bug showing that '/filter' toggles filter on
and off, while in 1.2.2 one use '/filter on' and '/filter off' for
that.

Beginnings of putting regular expressions defining filter in @filter
array.  All regular expressions are yet embedded literally (hardcoded)
in isFiltered() subroutine.  Added /~&~&~/ as filter rule.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>