All of the masked store calls were inhibiting putting values into
registers, which in turn led to a lot of unnecessary stack traffic.
This approach seems to give better code in the end.
Fix RNG state initialization for 16-wide targets
Fix a number of bugs in reduce_add builtin implementations for AVX.
Fix some tests that had incorrect expected results for the 16-wide
case.
Emit calls to masked_store, not masked_store_blend, when handling
masked stores emitted by the frontend.
Fix bug in binary8to16 macro in builtins.m4
Fix bug in 16-wide version of __reduce_add_float
Remove blend function implementations for masked_store_blend for
AVX; just forward those on to the corresponding real masked store
functions.
