Specifies file saving modes for IG_mpi_file_save function.

Values:

IG_MPI_SAVE_OVERWRITE	Replace all existing pages with new ones.
IG_MPI_SAVE_APPEND	Append new pages at the end of file.
IG_MPI_SAVE_INSERT	Insert pages into the file at the specified index.
IG_MPI_SAVE_REPLACE	Replace pages starting from the specified page index.