Review GTime, GTimeReference, GGti, GEbounds and GPhoton classes.

GTime
  The secs() method now returns a const reference.

GTimeReference
  The load constructor and the read() and write() methods take
  a const reference instead of a pointer.

GGti
  The read() and write() methods now use references instead of
  pointers. The clobber argument in the save() method is passed
  as const reference.

GEbounds
  The read() and write() methods now use FITS references instead
  of pointers. The clobber argument in the save() method is passed
  as const reference.

GPhoton
  Add mcid argument to Photon constructor (defaults to -1).
The FITS read() and write() methods now take reference instead of pointers.