QtIFW

Enable building IFW with Squish support

Change enables building IFW with Squish support by passing SQUISH_PATH
to qmake when building IFW. Also enables runtime change of Squish port
with command line option --squish-port <port number>. If no port is set,
default port 11233 is used to attach to Squish.

Change-Id: I4821b360031df66968d3592886c2e45598e1b097
Reviewed-by: Iikka Eklund <iikka.eklund@qt.io>
Reviewed-by: Antti Kokko <antti.kokko@qt.io>
Reviewed-by: Johanna Äijälä <johanna.aijala@qt.io>