vchoi_fork

Preliminary checkins for implementation done so far:
1) Public routines: H5Pget/set_vfd_swmr_config
2) Public routine: H5Fvfd_swmr_end_tick
3) Initialization when opening a file with VFD SWMR writer
4) Tests in test/vfd_swmr.c for VFD SWMR
5) Fix a bug in src/H5Fint.c: when error is encountered after the root group is created
Note the following:
--This is WORK IN PROGRESS and will subject to change as implementation goes.
--There is test failure form enc_dec_plist.c: I will fix this when changes to the property list are settled.
--The branch is updated with the latest from develop as of 8/14/2018