Decoupling Architectural-specific Code (#35)

* add headers for generic arch implementation

* restructure the arch-dependent file, better separation

* populate generic architecture for templating

* more cleaning and refactoring to keep things stay decoupled
* allow architectural specific code to override klib functions.

* merge lib/ into klibc for uniformity

* add x86 specific crc32 implementation, require SSE4 extension

* rename isr_param to more general hart_state

* isolate: direct reference of memeber inside hart_state

* isolate the hstate dumping part of trace.h.

* general clean up

* decouple gdbstub from architectual code.

* fix the trace_log missing component name
* add reg_t to shadow the explicit typed register value

* rename hart_change_execution to hart_flow_redirect