* Cloned iframe stack management from x86.
* Reimplemented arch_thread_{get,set}_current_thread(). The
thread structure is stored in SPRG2. It is set to NULL in
arch_cpu_preboot_init(), now. A non-null current thread
causes all kinds of undesired behavior in early boot code.
* We establish the address space mappings we know from the
Open Firmware as areas. At least those in kernel address
space. The ones in userland address space are tougher.
Fortunately on my Mac mini there aren't any save the
boot_loader stack, which is not needed any longer anyway.
* Added stack trace support to the kernel debugger. Mostly
cloned and adjusted the x86 code. Some bits are still
missing, like stack traces for other threads.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@15890 a95241bf-73f2-0310-859d-f6bbb57e9c96
