sh: Test that the read builtin passes through all byte values

except NUL, newline and backslash.

This also passes on stable/8.

tools/regression/bin/sh/builtins/read5.0

@@ -0,0 +1,32 @@
+# $FreeBSD$
+
+unset LC_ALL
+LC_CTYPE=en_US.ISO8859-1
+export LC_CTYPE
+
+# Note: the first and last characters are not whitespace.
+# Exclude backslash and newline.
+bad1=`printf %03o \'\\\\`
+bad2=`printf %03o \''
+'`
+e=
+for i in 0 1 2 3; do
+	for j in 0 1 2 3 4 5 6 7; do
+		for k in 0 1 2 3 4 5 6 7; do
+			case $i$j$k in
+			000|$bad1|$bad2) continue ;;
+			esac
+			e="$e\\$i$j$k"
+		done
+	done
+done
+e=`printf "$e"`
+[ "${#e}" = 253 ] || echo length bad
+
+r1=`printf '%s\n' "$e" | { read -r x; printf '%s' "$x"; }`
+[ "$r1" = "$e" ] || echo "read with -r bad"
+r2=`printf '%s\n' "$e" | { read x; printf '%s' "$x"; }`
+[ "$r2" = "$e" ] || echo "read without -r bad 1"
+IFS=
+r3=`printf '%s\n' "$e" | { read x; printf '%s' "$x"; }`
+[ "$r3" = "$e" ] || echo "read without -r bad 2"