JPSSnagg

Add presorting of the input files according to the date and start time fields in the file name (dYYYYMMDD_THHMMSSS).
    nagg_presort_infiles.c:     new file with new function nagg_sort_inputfiles(), regex functions to select the fields, and comparison function to pass th HDqsort.
    nagg.h                      add prototype for the new function.
    nagg_main.c                 call the new function before calling nagg_get_granules() to read granules in input files.
    Makefile.*                  add new file

Tested jam and platypus, gcc and icc.