add LLVMCodeGenTest
fix LLVMCodeGen
Merge commit 'ef6e67c8d2ab6dd316126202f7e3960a902b1f71'
fix conflict
support ApplyNode
Merge commit '22607dedbae18caa126fd89bc64659b6da086ed1'
fix conflict
several fix
Merge commit '43cf0161d123d2733701e25c331995dd2d766293'
several fix
Merge commit '798514fa32cc790f9caacd11d981b4f28f3c57bc'
pass	testReturnConst, testAddOne
		testIf, testMethodCall
		testTopLevelExpr
pass testFib
several fix
Merge commit '76d0921f65b6a7b61843bbd513b5e7c55565b7d9'