Revert "Revert "support for 'half' types in sksl, plus general numeric type improvements""

This reverts commit 0e9605542444a7653359f4fc610f7620df9f6313.

Bug: skia:
Change-Id: Id45d091c1950887316c901ed9c9281181f346bcf
Reviewed-on: https://skia-review.googlesource.com/29602
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
17 files changed