Don't disable CR-to-NL translation when waiting for data to arrive.

A difference between the old and the new TTY layer is that the new
implementation does not perform any post-processing before returning
data back to userspace when calling read().

sh(1)'s read turns the TTY into a raw mode before calling select(). This
means that the first character will not receive any ICRNL processing.
Inherit this flag from the original terminal attributes.

Even though this issue is not present on RELENG_*, I'm MFCing it to make
sh(1) in jails behave better.

PR:		bin/129566
MFC after:	2 weeks

bin/sh/miscbltin.c

@@ -147,6 +147,7 @@ readcmd(int argc __unused, char **argv __unused)
 		if (tcgetattr(0, &told) == 0) {
 			memcpy(&tnew, &told, sizeof(told));
 			cfmakeraw(&tnew);
+			tnew.c_iflag |= told.c_iflag & ICRNL;
 			tcsetattr(0, TCSANOW, &tnew);
 			tsaved = 1;
 		}