device: Add -device and -device-option to configure

device: Add -device and -device-option to configure

For some reference platforms and SDKs we will need to pass in
extra paths. Currently users have to modify the mkspec to adjust
paths or set environment variables that will be picked up.

This change introduces the -device <name> and -device-option
<key=value> option. The key value pairs will be written to a
qdevice.pri and can be used by the qmake.conf of the device spec.

The reason to not save the key value pairs in qconfig.pri is
becase of the fact that the device spec loads the qdevice.pri
earlier than the qconfig.pri. qdevice.pri allows the mkspec
to set the compiler flags and qconfig.pri allows configure to
add to those compiler flags.

Done-with: Holger Freyther

Change-Id: I931a197b8be72397e1eedfee09502eefc01c9d4f
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>
Reviewed-by: Johannes Zellner <johannes.zellner@nokia.com>
Reviewed-by: Donald Carr <donald.carr@nokia.com>