Perform some cleanup in libmadx.pxd
Perform some cleanup in libmadx.pxd

- for simplicity list only the struct members that are needed
- for maintainability list the struct members in the correct order
- for explicity always use the most specific header file name
- for consistency use common spacing for pointer types

pymad/jpymad,pymad/jpymad,pymad/cpymad,pymad/cpymad,pymad/jpymad