swift234

Revert "Enumerate all accessed locations before running data flow for dead store elimination. This helps to resize the bit vector to the appropriate size and we do not need to keep resizing them as new locations are discovered. Instrument shows a non-trivial amount of time is spent in bitvector resizing in dead store elimination."

This reverts commit r32362 because it's implicated in breaking many
tests on the simulator.

Swift SVN r32366