defconfig: add beaglexm defconfig

add defconfig for BeagleBoard xM.
powervr: add powervr virtual package
ti-gfx: add new package

adds accelerated GPU support for the OMAP35xx, AM35xx, AM37xx, DM37xx,
AM387x, C6A814x, AM389x, C6A816x, and AM335x platforms.
qt: add powervr and opengl

Use the following to test:
/usr/share/qt/examples/opengl/hellogl_es2/hellogl_es2 -qws -display powervr
defconfigs: demo defconfig for showing sgx on beaglexm
gst1-plugins-bad: rework eglglessink for ti-gfx
libglib2: needs threads

See autobuild failures

http://autobuild.buildroot.net/results/d1fb882fe4d22a17bdd438360da515011dda2b30/build-end.log
http://autobuild.buildroot.net/results/b66e807769ead5caa3e3b6312e9f7c35c14eafe7/build-end.log
http://autobuild.buildroot.net/results/9c3fa0c5003a6369e70bfe6d611f7d745742a8c7/build-end.log