make sure that we don't call basic_streambuf::gbump with a value bigger than INT_MAX, since it only takes an int. Related to, but not quite the same as PR33725

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@308880 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed