Shrink the builtinID down by 3 bits, allowing all the bitfields to fit in 32-bits, shrinking IdentifierInfo by a word.
Shrink the builtinID down by 3 bits, allowing all the bitfields to
fit in 32-bits, shrinking IdentifierInfo by a word.

This shrinks the total size of the identifier pool from 
1817264 to 1634428 bytes (11%) on carbon.h.


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@42719 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang