[WebAssembly] Add SIMD integer min/max builtins
Although SIMD integer min/max operations can be expressed using the ?:
operator in C++, that operator is disallowed for vectors in C. As a
workaround, this change introduces new WebAssembly-specific builtin
functions that lower to the desired vector icmp/select sequences.
Reviewers: aheejin, dschuff, kripken
Subscribers: sbc100, jgravelle-google, sunfish, cfe-commits
Differential Revision: https://reviews.llvm.org/D75770