shtests: More speedups; also fix xtrace (re: 734e5953)

This reduces a bunch more unnecessarily long sleeps to give
asynchronous processes time to run, etc. (No, we don't need to be
compatible anymore with your cool 1985 Intel 80386DX 16 MHz
battlestation...) Running the test suite is almost tolerable now,
making me much more likely to actually run the regression test
suite and catch my own regressions.

In addition, there are various fixes to make the test suite
compatible with 'set -x' ('set -o xtrace') so that you can now
actually *use* the documented 'bin/shtests -x' option. Recommend
combining with '-p' to avoid tracing everything three times.

I've also added a really useful $PS4 trace prompt to shtests that
traces pretty much everything there is to trace. (It does use
expansions that modify ${.sh.match}, which affected several tests,
particularly in tests/substring.sh; for those we need to set a
temporary simpler $PS4.)

(cherry picked from commit c3a5d47cfe880b526cabb5370ddaced0e8626acd)

src/cmd/ksh93/tests/coprocess.sh

@@ -109,7 +109,7 @@ do
 	$cat |&
 	!
 	chmod +x $file
-	sleep 10 |&
+	sleep 1 |&
 	$file 2> /dev/null || err_exit "parent $cat coprocess prevents script coprocess"
 	exec 5<&p 6>&p
 	exec 5<&- 6>&-
@@ -119,15 +119,15 @@ do
 	cop=$!
 	exp=Done
 	print -p $'print hello | '$cat$'\nprint '$exp
-	read -t 5 -p
-	read -t 5 -p
+	read -t 1 -p
+	read -t 1 -p
 	got=$REPLY
 	if	[[ $got != $exp ]]
 	then	err_exit "${SHELL-ksh} $cat coprocess io failed -- got '$got', expected '$exp'"
 	fi
 	exec 5<&p 6>&p
 	exec 5<&- 6>&-
-	{ sleep 4; kill $cop; } 2>/dev/null &
+	{ sleep .4; kill $cop; } 2>/dev/null &
 	spy=$!
 	if	wait $cop 2>/dev/null
 	then	kill $spy 2>/dev/null
@@ -140,15 +140,15 @@ do
 	echo line2 | grep 'line1'
 	} |&
 	SECONDS=0 count=0
-	while	read -p -t 10 line
+	while	read -p -t 1 line
 	do	((count++))
 	done
-	if	(( SECONDS > 8 ))
+	if	(( SECONDS > .8 ))
 	then	err_exit "$cat coprocess read -p hanging (SECONDS=$SECONDS count=$count)"
 	fi
 	wait $!
 	
-	( sleep 3 |& sleep 1 && kill $!; sleep 1; sleep 3 |& sleep 1 && kill $! ) ||
+	( sleep .3 |& sleep .1 && kill $!; sleep .1; sleep .3 |& sleep .1 && kill $! ) ||
 		err_exit "$cat coprocess cleanup not working correctly"
 	{ : |& } 2>/dev/null ||
 		err_exit "subshell $cat coprocess lingers in parent"
@@ -166,7 +166,7 @@ do
 			wait $!
 		done
 		print
-	) 2>/dev/null | read -t 10 r
+	) 2>/dev/null | read -t 1 r
 	[[ $r == $e ]] || err_exit "$cat coprocess timing bug -- expected $e, got '$r'"
 	
 	r=
@@ -174,21 +174,21 @@ do
 		integer i
 		for ((i = 1; i <= N; i++))
 		do	print $i |&
-			sleep 0.01
+			sleep 0.001
 			r=$r$($cat <&p)
 			wait $!
 		done
 		print $r
-	) 2>/dev/null | read -t 10 r
+	) 2>/dev/null | read -t 1 r
 	[[ $r == $e ]] || err_exit "$cat coprocess command substitution bug -- expected $e, got '$r'"
 	
 	(
 		$cat |&
-		sleep 0.01
+		sleep 0.001
 		exec 6>&p
 		print -u6 ok
 		exec 6>&-
-		sleep 2
+		sleep .2
 		kill $! 2> /dev/null
 	) && err_exit "$cat coprocess with subshell would hang"
 	for sig in IOT ABRT
@@ -198,12 +198,12 @@ do
 					pid=\$!
 					trap "print TRAP" \$sig
 					(
-						sleep 2
+						sleep .2
 						kill -\$sig \$\$
-						sleep 2
+						sleep .2
 						kill -\$sig \$\$
 						kill \$pid
-						sleep 2
+						sleep .2
 						kill \$\$
 					) &
 					while	read -p || ((\$? > 256))
@@ -218,7 +218,7 @@ do
 	done
 	
 	trap 'sleep_pid=; kill $pid; err_exit "$cat coprocess 1 hung"' TERM
-	{ sleep 5; kill $$; } &
+	{ sleep .5; kill $$; } &
 	sleep_pid=$!
 	$cat |&
 	pid=$!
@@ -232,7 +232,7 @@ do
 	[[ $sleep_pid ]] && kill $sleep_pid
 	
 	trap 'sleep_pid=; kill $pid; err_exit "$cat coprocess 2 hung"' TERM
-	{ sleep 5; kill $$; } &
+	{ sleep .5; kill $$; } &
 	sleep_pid=$!
 	$cat |&
 	pid=$!
@@ -244,7 +244,7 @@ do
 	[[ $sleep_pid ]] && kill $sleep_pid
 	
 	trap 'sleep_pid=; kill $pid; err_exit "$cat coprocess 3 hung"' TERM
-	{ sleep 5; kill $$; } &
+	{ sleep .5; kill $$; } &
 	sleep_pid=$!
 	$cat |&
 	pid=$!