buildroot

package: add mediastreamer

It doesn't really need C++ support on Linux, but the configure script
checks for it (and fails if not available), and the package is not easy
to autoreconf as there's C++ source files for Android/Windows, causing
automake to fail if AC_PROG_CXX isn't set.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>