x86[_64]: Separate bootloader and kernel GDT and IDT logic

From now on bootloader sets up its own minimal valid GDT and IDT. Then
the kernel replaces them with its own tables.

x86: Let each CPU have its own GDT

kernel: Use SMP_MAX_CPUS instead of B_MAX_CPU_COUNT

kernel: Track load produced by interrupt handlers

Add support for pthread_attr_get/setguardsize()

* Added the aforementioned functions.
* create_area_etc() now takes a guard size parameter.
* The thread_info::stack_base/end range now refers to the usable range
only.

Fix kernel build with KDEBUG_LEVEL 0.

Cleaner separation of 32-/64-bit specific CPU/interrupt code.

Renamed {32,64}/int.cpp to {32,64}/descriptors.cpp, which now contain
functions for GDT and TSS setup that were previously in arch_cpu.cpp,
as well as the IDT setup code. These get called from the init functions
in arch_cpu.cpp, rather than having a bunch of ifdef'd chunks of code
for 32/64.

x86[_64]: Separate bootloader and kernel GDT and IDT logic

From now on bootloader sets up its own minimal valid GDT and IDT. Then
the kernel replaces them with its own tables.

x86: Let each CPU have its own GDT

kernel: Use SMP_MAX_CPUS instead of B_MAX_CPU_COUNT

kernel: Track load produced by interrupt handlers

Add support for pthread_attr_get/setguardsize()

* Added the aforementioned functions.
* create_area_etc() now takes a guard size parameter.
* The thread_info::stack_base/end range now refers to the usable range
only.

Fix kernel build with KDEBUG_LEVEL 0.

Cleaner separation of 32-/64-bit specific CPU/interrupt code.

Renamed {32,64}/int.cpp to {32,64}/descriptors.cpp, which now contain
functions for GDT and TSS setup that were previously in arch_cpu.cpp,
as well as the IDT setup code. These get called from the init functions
in arch_cpu.cpp, rather than having a bunch of ifdef'd chunks of code
for 32/64.