ConsoleBuf: Use a custom std::streambuf for console output on Windows

Currently Microsoft's C++ libraries implementation of std::cout/cerr
can't output Unicode characters but only ASCII or ANSI if locale is set
so we implement and use our own ConsoleBuf which can output Unicode
characters to console and it doesn't matter what locale or console's
codepage is set.

Change-Id: I33053aa229796e84088aa3beb0ebe8bdbebaf3d1