Avoid including intrin.h from MathExtras.h

This is repeatably worth 0.3s compile time on MathExtras.cpp. This is a
very popular header, and it basically pulls all Intel intrinsics into
every LLVM TU. Let's not do that.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@335406 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed