added long option to specify log filesize
added volatility option to work_queue_worker, to simulate failure
with "reliability".
Check for available disk space on each pass through the main loop,
so as to handle tasks that consume space quickly on output.
Display space error in units of megabytes.

Conflicts:
	dttools/src/work_queue_worker.c
Fixed parsing to be consistent with help message: disk space limit is expressed as plain number without units.
Previous code accepted units but didn't handle them correctly.
Add debug msg when resetting execv syscall number.
Merge branch 'master' of github.com:cooperative-computing-lab/cctools

Conflicts:
	dttools/src/work_queue_worker.c
Fixed bug: buffer_printf appends to the buffer, so buffer_tostring
is not needed (and caused a crash).