Summary: * Add expat and ncurses support for gdb-cross. * Rebase and create patches for crosstool-ng upstream. * Compare configurations difference between crosstool-ng and embedded toolchain.

Details: * Add expat and ncurses support for gdb cross. At this time, all the packages can be built for both Linux and Mingw32 host with baremetal target. * Rebase and create patches for crosstool-ng upstream. Patches are sent to Michael for review. * Compare configurations difference between crosstool-ng and embedded toolchain. To align the configuration, crosstool-ng * need (not necessary) --disable-nls for companion libs. * need make document. * need add --enable-newlib-register-fini config and enhance CFLAGS_FOR_TARGET for newlib. * need --disable-sim for gdb. * need multilib support (Can workaround for current implementation. Need improvement when it is fully supported).

Thanks! -Zhenqiang