skvx wip

 - remove ALWAYS_INLINE until we find we need it

 - make bit_puns explicit

 - implement everything recursively so, e.g.
   sqrt(float8) picks up sqrt(float4) when
   not otherwise specialized.

 - implement SSE specializations:
   of the operations I tested, only sqrt, rcp, and rsqrt
   needed any help.  The others look good as-is.

Change-Id: I1b679c7bd9a99f952272b118d7ade2469b55d604
Reviewed-on: https://skia-review.googlesource.com/c/190222
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>