JPSSnagg

Initial implementation of creating fill granules to call write_granules().
Program is dying in write_granules().  Proceed to commit so that Larry may
debug the failure.

nagg.h:
    added the Time_First_Ascend definition (not sure the value is correct).
nagg_posix.h:
    added some more functions used.
nagg_select_granules.c
    Initial implementation of init_fill_granules_array() and make_fill_granule()
    to support the creation of fill granules when needed.

Tested in dove (linux)--failing in write_granules.