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.

- memory management is now entirely handled by darshan-core for
  module records
    * when registering new records, darshan-core returns the
      corresponding buffer to write it to, rather than allowing
      module to determine this
- modules now decide whether darshan-core should track record
  names by passing either a valid name or NULL to the register
  function
    * this allows modules to register records that aren't really
      tracked by darshan-core
- only the POSIX module has been ported to new changes for this
  commit

also some code clean up to change references of record hash
to name hash to be more clear about what it is actually storing.

common value counters are sorted first by decreasing counts,
and then by decreasing size.

epilog will now skip on-node compression if only a single compute
node is used and will generate the final log file instead

dev-modular should be completely merged into mmap-dev branch

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

- modules now receive a memory buffer after successfully
registering with darshan-core. modules can request a specific
memory amount, but may not be honored depending on the configured
darshan memory limit
- split the previous register_record function into 2 parts:
    * lookup() -> lookup darshan_record_id corresp. to path name
    * register() -> register record_id & name with darshan-core
- register_record now returns true if the record added; false
otherwise (if module was out of memory or darshan is out of memory
for storing id->name mappings)