Add return ref test

Fixed unbox enum type to int type caused InvalidCastException

Remove old Variance tests

Fixed int to string conversion caused test fail

Fixed int to string conversion caused test fail

Add CIL Variance tests

Get modifier names through TypeSig

Remove modifiers for handle correctly CModOpt modifiers

Move MethodImpl CIL files

Move test CIL files

Remove illegal override test entries

Add CIL MethodImpl tests

Add CIL MethodImpl test sources

Remove old InterfaceFolding binaries

Replace call Console instructions to pop