[Change] Sync from 2006 code to 2011 code
[Change] Sencond sync to lab1 2011 code
[Change] Complete the function of mon_backtrace(), print more infomation: file name, func name, line number.
[Fix bug] print the function name in mon_backtrace properly.
[Change] Add color print support in console
[Change] Merge lab2 code
update lab2

Signed-off-by: h.t.jacky <h.t.jacky@gmail.com>
[Change] 1. Implement exercise 1 in lab2, boot_alloc(), page_init(), page_alloc(), page_free(); 2. Add mon_backtrace() in panic();
[Change] lab2: Exercise 4: Implement pgdir_walk, boot_map_region, page_lookup, page_remove and page_insert.
[Change] lab2 exercise5, complete mem_init() about paging machenism.
[Change] Add grade-functions.sh
[Change]Lab2 Challenges
[Merge] lab3 update.
[Change] Lab3 exercise 1, and fix some bugs in page_remove(),page_walk() and page_insert().
[Change] fix a bug in load_icode(), need to load back to kern_pgdir after load enviroment
[Change] Remove some debug information
[Change] Fix a bug when setting curenv.
[Change]Lab3 - Exercise 4: Initialize IDT
[Change] lab3- Exercise 5&6
[Change] lab3 - Challenge 1, add continue and singe step in monitor~