Changes in Conv*, Ld* and St* opcodes so that values with size < 4 bytes are extended to 4 bytes.
Implemented Not and Xor for values with size 8 bytes.
Added tests for bitwise operations, arithmetic operations and Conv* opcodes.
- Added test for Neg OpCode for float and double
- Conv.U8 wrongly changed the sign of double before converting it to ulong
- Div_Un, Add_Ovf and Add_Ovf_Un had code for floating point but they should not have that for ECMA specs