plugins: tty: possible out-of-bounds read in inotify_event parser

This is a major refactor to use the same construct as in the pidfile.so
plugin to parse kernel inotify events for when TTYs are added removed
from the system.

Found by Coverity Scan.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/tty.h

@@ -30,7 +30,6 @@
 #include <lite/queue.h>		/* BSD sys/queue.h API */
 
 #define TTY_MAX_ARGS 16
-#define EVENT_SIZE ((sizeof(struct inotify_event) + NAME_MAX + 1))
 
 struct tty {
 	LIST_ENTRY(tty) link;