Update SigComparer...
Update SigComparer...

- Add SubstituteGenericParameters option to enable MemberRef compares
  against MethodBase
- The CLR maps FnPtr to System.IntPtr. Update the code to make sure
  a FnPtr and a System.IntPtr compares equal when comparing our MethodSig
  to a MethodBase.

0xd4d/dnlib,picrap/dnlib,yck1509/dnlib,jorik041/dnlib,Arthur2e5/dnlib,modulexcite/dnlib,kiootic/dnlib,ilkerhalil/dnlib,ZixiangBoy/dnlib