GitLab

- eliminated 110 SLOC
- untested

- note: darshan-stdio module updates are still needed; this merge just
  updates the rest of the code and resolves conflicts

Merging mmap feature development branch back into master. Darshan
can now mmap its data structures to temporary log files at runtime to
protect against applications that do not call MPI_Finalize. Feature
can be enabled at configure time using '--enable-mmap-logs'.

A common record comparision/sort routine is now defined in
darshan-common which can be used by any modules with fixed-length
records and whose records first field is the darshan_base_record.
The comparison was also updated to sort secondarily by darshan
record identifier to resolve a potential bug in the way we have
traditionally sorted the records.

Conflicts:
	darshan-runtime/Makefile.in
	darshan-runtime/configure
	darshan-runtime/configure.in
	darshan-runtime/darshan.h
	darshan-runtime/lib/darshan-core.c
	darshan-runtime/lib/darshan-hdf5.c
	darshan-runtime/lib/darshan-mpiio.c
	darshan-runtime/lib/darshan-pnetcdf.c
	darshan-runtime/lib/darshan-posix.c
	darshan-util/Makefile.in
	darshan-util/darshan-convert.c
	darshan-util/darshan-logutils.c
	darshan-util/darshan-logutils.h
	darshan-util/darshan-parser.c

rather than using 'begin_shutdown', 'get_output_data', and
'shutdown', we combine all three into one shutdown routine.

Cleanup the structure and documenation of the code to be in sync
with the new mmap version of Darshan. In particular, I made sure
all extra mmap logic was properly ifdef wrapped so it's more clear
which portions of the code are responsible for implementing that
feature.

This interface provides some convenience functions for mapping
opaque record identifiers (could be a filename, file descriptor,
or any other type of file handle) to a corresponding runtime
structure referencing the actual file record. This runtime
structure should at least contain a pointer to the actual file
record, and can also persist arbitrary state for this record.