in emit.ml, support the branch instructions
make it easy to debug

make it easy to find where the pattern matching in Emit.g' is missing
rename SetF -> SetL and raise Not_supported_yet
can compile fib.ml(?)

support CallDir
repair tail_call
name $v0 reg_ret
fix the bug of slt instruction
delete jump to main label in first line
bug fix on branch
add library directory and linker.py
Merge branch 'master' of https://github.com/cpuex2014-4/compiler

Conflicts:
	emit.ml