Disable two failing tests for now.
Fix the return type of SIMD.float64x2.splat
Remove "use strict" from the polyfill

Applications may wish to use the SIMD polyfill without having
"use strict" applied to themselves.

We can use "use strict" in the benchmark though, to ensure that all the
code works under it.
Resync isTypedArray functions
Update int32x4's constructor comment
Simplify load and store polyfills
Whitespace consistency
Minor formatting tidying
Comment fixes
Merge pull request #76 from sunfishcode/master

Minor fixes and simplifications