Made JNA dependency version requirement more conservative

Use explicit Structure(Pointer, int) constructor instead of convenience
Structure(int) constructor.
Fix function names in Windows.

In WinSCard.h on Windows, some of the functions are actually macros that expand to the ascii or wide version. We use the ascii versions to match pcsclite, which is only ascii.
Fix for Windows x86_64; size of SCardContext should be Pointer.SIZE.

Previously, I assumed that SCardContext was always a NativeLong. This is correct on Linux, but wrong on Windows and Mac. All functions in Windows x86_64 would fail with error 6 (ERROR_INVALID_HANDLE) because I truncated the pointer. I did not notice any crashes on Mac, because it SCARDCONTEXT there is just a int32 that increments from 1.

Fix SCardContext to match the different headers: make it a subclass of IntegerType instead of Structure, and make it 32 bits on Mac, the same size as a pointer on Windows, and the same size as a long on Linux.