IOR version 4.0.0 release candidate 1

New major features:

• Add PMDK backend (Adrian Jackson)
• Add CHFS backend (Osamu Tatebe)
• Add AIO backend (Julian Kunkel)
• New S3 backend (Julian Kunkel)
• New md-workbench benchmark (Julian Kunkel)
• New BFS backend (Osamu Tatebe)
• Add GPUDirect Storage support (Julian Kunkel)

New minor features:

• Updated DAOS backend to match latest DAOS APIs (Mohamad Chaarawi)
• Updated HDF5 backend (Jordan Henderson)
• Improved Spectrum Scale hint support (Pidad D'Souza)
• Add CSV output (Sebastian Oeste)
• Improved Gfarm support (Osamu Tatebe)
• Updated HDFS backend
• MDTest now has a directory renaming test
• Add prologue/epilogue support (GUAN Xin)
• Add stronger randomized data using golden primes (Glenn K. Lockwood)
• Add dummy backend (Julian Kunkel)
• Improved CephFS support (Pablo Llopis)
• Improved PnetCDF support (Wei-keng Liao)

Bugfixes:

• Expansive fixes to mdtest correctness (Julian Kunkel)