SMP - Cpu local variables

- most global variables carry information which is specific to the
  local CPU and each CPU must have its own copy

- cpu local variable must be declared in cpulocal.h between
  DECLARE_CPULOCAL_START and DECLARE_CPULOCAL_END markers using
  DECLARE_CPULOCAL macro

- to access the cpu local data the provided macros must be used

	get_cpu_var(cpu, name)
	get_cpu_var_ptr(cpu, name)

	get_cpulocal_var(name)
	get_cpulocal_var_ptr(name)

- using this macros makes future changes in the implementation
  possible

- switching to ELF will make the declaration of cpu local data much
  simpler, e.g.

  CPULOCAL int blah;

  anywhere in the kernel source code

kernel/arch/i386/include/arch_proto.h

@@ -95,6 +95,11 @@ _PROTOTYPE( void frstor, (void *));
 _PROTOTYPE( unsigned short fnstsw, (void));
 _PROTOTYPE( void fnstcw, (unsigned short* cw));
 
+_PROTOTYPE(void __switch_address_space, (struct proc * p,
+						struct proc ** __ptproc));
+#define switch_address_space(proc)	\
+	__switch_address_space(proc, get_cpulocal_var_ptr(ptproc))
+
 /* protect.c */
 struct tss_s {
   reg_t backlink;