convert sext<*> like functions to sext_* functions
add 'execution_engine' as 'builder'
fix bug of SwitchGenerator
move method castTo to types and call them from TypeCaster; add compare and castTo support for TypeIDType
fix small bugs
fix bug of '>>', '<<', '>>=' and '<<=' translation
add function call support for 'swap_byte' and 'bits'; fix bug of 'findXXX'