PMDK Version 1.7

This release:

• Introduces new APIs in libpmemobj for managing space used by transactions.
  (see pmemobj_tx_log_append_buffer man page for details)
• Introduces new APIs in librpmem, splitting rpmem_persist into rpmem_flush
  and rpmem_drain, allowing applications to use the flush + drain model
  already known from libpmem. (libpmemobj does not use this feature yet)
• Optimizes large libpmemobj transactions by significantly reducing
  the amount of memory modified at the commit phase.
• Optimizes tracking of libpmemobj reservations.
• Adds new flags for libpmemobj's pmemobj_tx_xadd_range[_direct] API:
  POBJ_XADD_NO_SNAPSHOT and POBJ_XADD_ASSUME_INITIALIZED, allowing
  applications to optimize how memory is tracked by the library.

To support some of the above changes the libpmemobj on-media layout had
to be changed, which means that old pools have to be converted using
pmdk-convert >= 1.7.

Other changes:

• obj: fix merging of ranges when NOFLUSH flag is used (pmem/issues#1100)
• rpmem: fix closing of ssh connection (pmem/issues#995, pmem/issues#1060)
• obj: abort transaction on pmemobj_tx_publish failure

Internal changes:

• test: fault injection tests for pmemblk, pmemlog, and pmemobj
• test: improved Python testing framework
• test: support real pmem in bad blocks tests
• common: allow not building examples and benchmarks