ee: Handle EINTR when waiting for a character

Otherwise one can't easily attach gdb to ee.

Reviewed by:	bapt
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D57997

contrib/ee/ee.c

@@ -678,7 +678,11 @@ main(int argc, char *argv[])
 			 * issue
 			 */
 			if (wret == ERR)
+			{
+				if (errno == EINTR)
+					continue;
 				exit(0);
+			}
 			in = (int)win;
 
 			resize_check();