Implement capability to fold this:

Implement capability to fold this:
uint %test4(int %A, int %B) {
        %COND = setlt int %A, %B                ; <bool> [#uses=1]
        %result = cast bool %COND to uint               ; <uint> [#uses=1]
        ret uint %result
}
into a single cast instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3339 91177308-0d34-0410-b5e6-96231b3b80d8