Fix problem in getccu when ctrl-Z is entered.

getccu calls getchr which calls iread.
When ctrl-Z (SIGTSTP) is entered, iread sets sigs |= S_STOP
and returns READ_INTR. getchr then also returns READ_INTR.
As of 2d0abe8, getccu converts any negative value like READ_INTR
to a null char, which causes getccu to ignore the char and call
getchr again. Before 2d0abe8 we would retain the negative char
and exit the loop, but the char value was not used because the
fact that sigs is set would be checked first. It seems more
straightforward to just exit the getccu loop when sigs is set.

Related to #563.

NEWS

@@ -33,6 +33,8 @@
 
 * Fix ^X bug when output is not a terminal (github #558).
 
+* Fix bug where ^Z is not handled immediately (github #563).
+
 ======================================================================
 
 	Major changes between "less" versions 643 and 661

command.c

@@ -1015,7 +1015,7 @@ public void getcc_clear(void)
 static char getccu(void)
 {
 	int c = 0;
-	while (c == 0)
+	while (c == 0 && !ABORT_SIGS())
 	{
 		if (ungot == NULL)
 		{

version.c

@@ -1028,7 +1028,7 @@ v662  8/8/24    Fix build with --with-secure; improve true colors on Windows;
                 fix --header with short file; fix ^X bug when output is not tty.
 v663  8/16/24   Fix ^X bug when output is not a tty.
 v664  8/28/24   Fix Windows compile error, fix output bug on Windows with -Da.
-v665
+v665            Fix ^Z bug.
 */
 
 char version[] = "665x";