Since we had to modify HDF5/PnetCDF linker flags to work on Cray
by undefining appropriate symbols, we need to update the linker
options used in darshan-config. darshan-config linker options need
to include the stubs libraries and use '--start-group' and
'--end-group' flags to resolve the symbols correctly

this reorganization prevents darshan from being "enabled"
(i.e., accessible to modules) until the initialization
has completely finished.

- prevents inadverdent disabling of Darshan on some MPICH builds
- fixes #94

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

this indicates whether the log file is complete or only partially
written