[include] add stdint.h and extend sys/types.h
[include] register.h: include sys/types.h

The header file defines uint32_t type. Include that header to make REG32
macro work.
[include] debug.h: add DEBUG level
[platform][realview-pb] initial commit for enabling interrupts

- Add platform_init() declaration in include/platform.h
- Define platform_init() for realview-pb platform which calls
  platform_init_interrupts()
- Add platform_init_interrupts() for enabling GIC0.
- Call platform_init() in top kernel code.
[scripts] add run-realview script to run emulation easily