finish genForStmt
move all testcase into directory testcase/, add hw6 testcase supported by TA
mechanism changed: no codegen if code is semantic error
add variable initialization, some comments
add some comments, finish implicit type conversion in expression
finish short circuit in if/while/for condition
add function call parameter pass (without array)
merge passing function call parameter (without array).
add 5 testcase for hw6 codegen
bug fixed: assignment stmt has return value, openScope use equvalent op as assignment op
genstmt use genFor, genFor gen through multiple assign stmt(codition), pass parameter use addi
Merge branch 'KHL_debug'
update testcase
add testcase multiStmtFor.c
add parameter passing in function definition
update testcase, modify genAssignExpr for function call stmt