iostreams & file streams

Makes operator<< print volatile T* as a pointer rather than as bool.

Adds ios_base::noreplace for exclusive-mode file opening (O_EXCL).

Revises the wording of stream input operations (sentry, error handling).

Adds native_handle() to file streams and file buffers.

Makes istream::ignore with a char delimiter behave as expected.

Deprecates the iostream overloads for signed char and unsigned char.