REGRESSIONS update based on the morning's returns

Update to REGRESSIONS based on the morning's returns and some housecleaning:

Improvements:
* removed the general "Error running sub-test for studies/lsms/shemmy" which I think was fixed some time ago when Thomas changed the way start_test/sub_test report known failures

Regressions:
* added an entry for valgrind regressions that started Saturday, apparently due to standalone parallel iterators
* noted the sporadic failures of sub_test due to failed os.unlink calls on cygwin32 which are not resolved as hoped and added back dates for recent cases

Misc:
* tvandoren/enumerate is starting to pass, but hasn't worked its way out of the system yet, so I added an entry to track the remaining failing cases
* added a few recent dates to sporadic failures that happened to be in my inbox