Extended Description

After Chris' round of changes to SimplifyLibCalls, it is now missing an
optimization that it previously performed, as identified by this test case
failing:
FAIL: /proj/llvm/llvm-1/test/Transforms/SimplifyLibCalls/SPrintF.ll:
child process exited abnormally
%r4 = call i32 (i8*, i8*, ...)* @​sprintf( i8* %target_p, i8* %fmt1_p, i8*
%hello_p ) ; [#uses=1]
%r4.1 = call i32 (i8*, i8*, ...)* @​sprintf( i8* %target_p, i8* %fmt1_p, i8* %p
) ; [#uses=1]
%r5 = call i32 (i8*, i8*, ...)* @​sprintf( i8* %target_p, i8* %fmt2_p, i32 82 )
; [#uses=1]

Some of these are important for performance. For example, the first one should
be reduced to a few stores.