Add missing logging.cc, move s_log_impl to log.cc

Also replace use of variadic templates with variadic arguments. Not as
nice, but this makes modifications to the log function easier as it
doesn't require everything be rebuilt.
Replace by-ref arguments for by-value with quats, lines, and vectors.

This turns out to be slightly faster at best and, at worst, no
different. Mostly depends on how often a given address needs to be read
from.
Add string constructors for a few primitives.

Just uses snprintf internally, so nothing special here.
Add string_t::format.

Just a wrapper around snprintf that writes the output to a string's
data. Really just for convenience.
Make the string_t fixed_alignments const.
Add buffer_stream_t class.

Convenience class for reading raw data from a buffer.