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user can now give a config option or use a runtime environment
variable to control darshan's per module memory requirements.

use --with-max-records at configure time to change from default
of 2048 records

-darshan-core:
    - initializes darshan job data structures
    - creates log file
    - writes job info header
    - reduces which modules were used locally/globally
    - shut down and write out individual modules one by one

-darshan-posix:
    - register w/ darshan-core and allocate allowed memory
    - track open counter and timestamp for opened files
    - provide file record buffer at shutdown

Major TODOs:
    - shared file reductions (prefer reusable across modules)
    - register handles with darshan file_ids (prefer reusable)
    - generic compression of module buffers (zlib/bzip2)
    - write out map of filenames to darshan ids
    - modify darshan-util and add darshan-posix parser to read logs

-also, darshan core uses utlist to keep track of modules

New darshan-core source files which intercept MPI init/finalize,
initialize darshan job information, and first attempt at a POSIX
module.