Add line response feature

Add a simple line response feature to make it possible to send e.g. a
command string to your serial device and easily receive and parse a line
response.

This is a convenience feature for simple request/response interaction
based on lines. For more advanced interaction the socket feature should
be used instead.

The line response feature is detailed via the following options:

 -r, --response-wait

Wait for line response then quit. A line is considered any string ending
with either CR or NL character. If no line is received tio will quit
after response timeout.

Any tio text is automatically muted when piping a string to tio while in
response mode to make it easy to parse the response.

 --response-timeout <ms>

Set timeout [ms] of line response (default: 100).

Example:

Sending a string (SCPI command) to a test instrument (Korad PSU) and
print line response:

 $ echo "*IDN?" | tio /dev/ttyACM0 --response-wait
 KORAD KD3305P V4.2 SN:32477045

src/options.h

@@ -67,6 +67,9 @@ struct option_t
     bool hex_mode;
     unsigned char prefix_code;
     unsigned char prefix_key;
+    bool response_wait;
+    int response_timeout;
+    bool mute;
 };
 
 extern struct option_t option;