GitLab

Fixed when we emit the doc start (only if there already is a document in the stream, and we're about to emit a new node)

Renamed the base64 methods, and switched the EncodeBase64 one to return a string (to make it easy to use elsewhere)

Refactored the base64 binary to its own space with a unified class that (will) be used for parsing (in addition to emitting)

Fixed compiler error in iterator_base friend forward declaration in node on clang (and I hope MSVC), plus warnings on clang

Switched the utf bom checking to putback in the stream (instead of keeping a secondary buffer), which fixes a bug when there's only one ascii character