MEDIUM: log: write raw strings using lf_rawtext()

MEDIUM: log: write raw strings using lf_rawtext()

Make use of the previous commit to print strings that should not be
modified.

For instance, when +X option is provided, we have to print numerical
values in ASCII HEX form. For that, we used snprintf() to output the
result to the log output buffer directly, but now we build the string in
a temporary buffer of fixed-size and then print it using lf_rawtext()
which will take care of encoding options.

Because of this patch, we add a little overhead because we first generate
the text into a temporary variable and then use lf_rawtext() to print it.
Thus we have a double-copy, and this could have some performance
implications that were not yet evaluated. Due to the small number of bytes
that can end up being copied twice, we could be lucky and have no visible
performance impact, but if we happen to see a significant impact, it could
be useful to add a passthrough mechanism (to keep historical behavior)
when no encoding is involved.