Since Go 1.5, if a key expression in a map literal is itself a composite
literal, the type may be omitted. An & operation may be implied,
but was not generated, resulting in a type mismatch crash.
Added regression test.
Also, added missing intrinsic math.hasSSE4 to interpreter.
Fixes issue 13341
Change-Id: I6a5e560460cdcac295a500a3fc3738cbe8aa5853
Reviewed-on: https://go-review.googlesource.com/17123
Reviewed-by: Robert Griesemer <gri@golang.org>
977844c7af