version of clamped vector load from nick-sandbox
updated clamped vector load code to use IR node make methods
test code for clamped vector load, for posterity
removing test app
Merge branch 'master' into clamped-vector-load
removed print statements and added a few comments to clamped vector load
removed environment variable check
Merge branch 'master' into clamped-vector-load
merged with master and nick-sandbox
removed print statements
removed environment variable check in clamped vector load
Having the last pass be CSE pulled out constants that mess up codegen
Took Load object off stack.
Added a performance test for clamped vector load.
Removed errant return 0
Messed with the schedule for interpolate some more
Bounds inference more aggressive

Previously it was giving up on const expressions, instead of
just returning them
Found several bugs in clamped load detection. Disabled for now.
Don't lift out calls to current_time

Need a better solution for side-effecting calls in the future.
Added a vector test case to IRMatch