Add support for BB10 input method framework

Added input method support for the BB10 variant of Qt to the extent
possible using standard Qt APIs.  This adds support for text predictions
and entry of languages such as Chinese.

Change in interface to QQnxAbstractVirtualKeyboard was made because it
is felt the new one is slightly nicer.  It doesn't appear safe to
assume the focus object has a particular property and in fact in my tests
the code failed to work.

In some cases the code uses variable and function naming at odds with
normal Qt coding standards.  This has been done for functions called
and data provided by the BB10 input system as for those of us who
need to maintain such things, it makes their meaning considerably
clearer.

While qqnxinputcontext_imf.cpp was used as an initial base for
development one can consider the new version as largely new code. I
don't believe the original version was ever complete and in any event
would not compile.

Change-Id: I09470801ffa237cee67da40c0b3d02ed5c77531e
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>
Add configuration for building with imf support on QNX

Avoid need to modify qnx.pro in src/plugins/platforms/qnx to
build with imf support.  By default detects if necessary headers
and libraries are available.  Can also be explicitly requested or
disabled with -imf and -no-imf options.

Change-Id: I3f9780fc189a33e4c93fb4f950111121f8e947c3
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>