This SO question:  http://stackoverflow.com/questions/15344402/how-can-i-read-a-0xff-in-a-file-with-libc-istream-iterator/15347225#15347225 highlighted the lack of a cast in the implementation of std::cin.  Added.  I unfortunately don't have a test case to add to the suite since this bug only shows itself when using std::cin.  The current testsuite setup does not have a way a good way to test std::cin.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@176822 91177308-0d34-0410-b5e6-96231b3b80d8