sh: First support code of SuperH.

CREDITS

Makefile

common/cmd_bootm.c

cpu/sh4/Makefile

cpu/sh4/config.mk

cpu/sh4/cpu.c

cpu/sh4/interrupts.c

cpu/sh4/start.S

cpu/sh4/time.c

cpu/sh4/watchdog.c

drivers/Makefile

drivers/serial_sh.c

examples/Makefile

examples/stubs.c

include/asm-sh/bitops.h

include/asm-sh/byteorder.h

include/asm-sh/cpu_sh4.h

include/asm-sh/cpu_sh7750.h

include/asm-sh/global_data.h

include/asm-sh/io.h