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.

/*
 * Data structures for parsing structured responses to AT commands
 */

struct resp_field {
	int		type;
	unsigned	num;
	char		*str;
};

#define	RESP_FIELD_EMPTY	0
#define	RESP_FIELD_NUMBER	1
#define	RESP_FIELD_STRING	2