glue: Proper support for -http-proxy option. This adds the required glue code to make -http-proxy option work, by injecting the AndroidEmu HTTP proxy implementation into the SLIRP stack at emulation setup time. + Remove -http-proxy from the list of QEMU2 options, it is not needed because the corresponding initialization can be performed directly in android-qemu2-glue/main.cpp instead. Change-Id: Ia972b7882ebf00a379ed9536e93e44551e3b0160