qtbase: remove gstreamer packageconfig

Nothing in qtbase uses gstreamer so the configure option was removed on the way
to 5.2 [1]. Fixes:

| -no-gstreamer: invalid command-line switch

[1] https://qt.gitorious.org/qt/qtbase/commit/e25a4faf4a33a758a51c1b96dfdead2f1675ccd7

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
qtjsbackend: remove for git versions

Found in [1]:
Qt Qml is now using its own built-in Javascript engine and does not depend on
V8 anymore. As such the QtJSBackend shared library has disappeared.

[1] http://blog.qt.digia.com/blog/2013/09/30/qt-5-2-alpha-available/

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
qtbase: fix paths in packageconfig *.pc files

include- and lib-paths contained build-sysroot paths

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>