hush: implement -d DELIM option for 'read'

The POSIX standard only requires the 'read' builtin to handle '-r':
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/read.html

However, Bash introduced the option '-d <DELIM>' to override IFS for
just one invocation, and it is quite useful.

We already support this in ash, let's add it to hush, too.

function                                             old     new   delta
builtin_read                                         263     284     +21
.rodata                                           163587  163589      +2
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 23/0)               Total: 23 bytes

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/hush.c b/shell/hush.c
index 8dc5316..af3b95b 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -352,6 +352,7 @@
 #define BASH_SOURCE        ENABLE_HUSH_BASH_COMPAT
 #define BASH_HOSTNAME_VAR  ENABLE_HUSH_BASH_COMPAT
 #define BASH_TEST2         (ENABLE_HUSH_BASH_COMPAT && ENABLE_HUSH_TEST)
+#define BASH_READ_D        ENABLE_HUSH_BASH_COMPAT
 
 
 /* Build knobs */
@@ -9434,13 +9435,20 @@
 	char *opt_p = NULL;
 	char *opt_t = NULL;
 	char *opt_u = NULL;
+	char *opt_d = NULL; /* optimized out if !BASH */
 	const char *ifs;
 	int read_flags;
 
 	/* "!": do not abort on errors.
 	 * Option string must start with "sr" to match BUILTIN_READ_xxx
 	 */
-	read_flags = getopt32(argv, "!srn:p:t:u:", &opt_n, &opt_p, &opt_t, &opt_u);
+	read_flags = getopt32(argv,
+#if BASH_READ_D
+		"!srn:p:t:u:d:", &opt_n, &opt_p, &opt_t, &opt_u, &opt_d
+#else
+		"!srn:p:t:u:", &opt_n, &opt_p, &opt_t, &opt_u
+#endif
+	);
 	if (read_flags == (uint32_t)-1)
 		return EXIT_FAILURE;
 	argv += optind;
@@ -9454,7 +9462,8 @@
 		opt_n,
 		opt_p,
 		opt_t,
-		opt_u
+		opt_u,
+		opt_d
 	);
 
 	if ((uintptr_t)r == 1 && errno == EINTR) {