Incorrect mixing of character and byte positions in parser

[brson]

I am doing some refactoring of the codemap in order to make some parser changes, and in the process adding types for character and byte positions. There are several places that use both together incorrectly. Will add FIXME's as I find them.

[brson]

It looks like this only happens in trim_whitespace_prefix_and_push_line

[graydon]

non-critical for 0.6, de-milestoning

[catamorphism]

Nominating for milestone 5, production-ready

[graydon]

just a bug, removing milestone/nomination.