[analyzer] If a C string length is UnknownVal, clear any existing length binding. No tests yet because the only thing that sets string length is strcpy(), and that needs some work anyway.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133044 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed