Make the altivec intrinsics that require immediate constant propagation macros rather than functions.
Make the altivec intrinsics that require immediate constant propagation
macros rather than functions.

Unfortunately couldn't come up with a simple testcase that didn't need
code generation to verify what was going on.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@270625 91177308-0d34-0410-b5e6-96231b3b80d8

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