Print warnings to stderr instead of stdout
Merge pull request #179 from jansel/master

Print warnings to stderr instead of stdout
Fix side effects test to have a dependence on all results from extern call

Otherwise llvm is clever and only does the last one.
Move all allocas to the top of the function

This means we don't need to do explicit stacksave/stackrestore. This makes
foo.compute_at(bar, x) faster, because it includes less stack-related junk.
Stopped regenerating initmod/msvc.cpp on every build
Converted abs to an intrinsic, and made it return unsigned.
Added a test for bounds of abs
Add code to handle an undefined bound in new abs bounds reasoning.
Add test case for above.
Typo fix.
Abs of something unbounded below but bounded above should be unbounded above.
Merge branch 'master' into skip_stages