[Sanitizer] More fixes to scanf interceptor: stub support for %s, support for %[...] directive

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@173451 91177308-0d34-0410-b5e6-96231b3b80d8
[msan] Tests for ICmp handling.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@173456 91177308-0d34-0410-b5e6-96231b3b80d8