mel: use gstreamer 0.10, not 1.0, for qtwebkit

Without this, all our builds including qt5 components resulted in building
both gstreamer versions, which caused sysroot and shlibs provider conflicts,
as well as slowing down our builds.

JIRA: SB-2713

Signed-off-by: Christopher Larson <kergoth@gmail.com>
Merge pull request #160 from kergoth/sb-2713

mel: use gstreamer 0.10, not 1.0, for qtwebkit