QtIFW

Allow to check for IFW version in code

Rename the IFW_VERSION to IFW_VERSION_STR, and add a new IFW_VERSION
define that encodes the version in hex. This follows the pattern of
QT_VERSION and QT_VERSION_STR, and allows easy checking of the IFW
version e.g. in macros.

Change-Id: I232c8aa53c9a04522810208cdd1ac595d8676879
Reviewed-by: Karsten Heimrich <karsten.heimrich@theqtcompany.com>