Added code to initialize processor specific data.
Fixed a bug that hungs up i7-4770K w/ Z87.
Implemented IPI to signal tick-less APs from tick-full BSP.
Moved scheduler-related code to sched.c.
Removed unused code.
Fix two critical bugs: 1) invalid movw -zshx1b,%rcx operation (must be movq) in asm.s before rdmsr, and 2) dead-locks of spinlock during interrupt handlers (this must be fixed soon). This commit also includes implementation of multitasking codes.