This simplifies analysis and borrow-checking because liveness at the
resume point can always be simply propagated.
Later on, the "dead" Resumes are removed.
This commit allocates a builder to running wasm32 tests on Travis. Not all test
suites pass right now so this is starting out with just the run-pass and the
libcore test suites. This'll hopefully give us a pretty broad set of coverage
for integration in rustc itself as well as a somewhat broad coverage of the llvm
backend itself through integration/unit tests.
