rvinterf: begin change to backslash escape output format Right now throughout the rvinterf suite, any time we emit output that is expected to be ASCII, but may contain non-printable garbage, we use 'cat -v' form of garbage character representation. Unfortunately, this transformation is lossy (can't be reversed 100% reliably in the user's wetware), hence we would like to migrate to C-style backslash escapes, including doubling of any already-present backslashes - this escape mechanism is lossless. Begin this change by converting the output of RV and L1 traces in rvinterf and rvtdump.