unicore32-softmmu: Add unicore32-softmmu build support

This patch adds unicore32-softmmu build support, include configure,
makefile, arch_init, and all missing functions needed by softmmu.
Although all missing functions are empty, unicore32-softmmu could
be build successfully.
By 20120804: change QEMU_ARCH_UNICORE32 to 0x4000

Signed-off-by: Guan Xuetao <gxt@mprc.pku.edu.cn>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>