Fix freeze in config's interrupt trap with some shells

With bash and zsh, the trap on the 5 second read does respond, but
doesn't break out of the read.  What's worse is that it takes away the
5 second timer, and therefore has the read hang indefinitely and
(almost) unbreakable.

Having the trap do 'exit 0' after reseting the tty params has it break
out of read and continue with the configuration.

Other shells do not appear to have the issue described here, but
neither does the extra 'exit 0' appear to harm them.

Reviewed-by: Andy Polyakov <appro@openssl.org>

config

diff --git a/config b/config
index ae349ec..fb24a5d 100755
--- a/config
+++ b/config
@@ -480,7 +480,7 @@
 	echo "         invoke '$THERE/Configure irix64-mips4-$CC' *manually*."
 	if [ "$TEST" = "false" -a -t 1 ]; then
 	  echo "         You have about 5 seconds to press Ctrl-C to abort."
-	  (trap "stty `stty -g`" 2 0; stty -icanon min 0 time 50; read waste) <&1
+	  (trap "stty `stty -g`; exit 0" 2 0; stty -icanon min 0 time 50; read waste) <&1
 	fi
         #CPU=`(hinv -t cpu) 2>/dev/null | head -1 | sed 's/^CPU:[^R]*R\([0-9]*\).*/\1/'`
         #CPU=${CPU:-0}
@@ -499,7 +499,7 @@
 	    echo "         invoke '$THERE/Configure darwin64-ppc-cc' *manually*."
 	    if [ "$TEST" = "false" -a -t 1 ]; then
 	      echo "         You have about 5 seconds to press Ctrl-C to abort."
-	      (trap "stty `stty -g`" 2 0; stty -icanon min 0 time 50; read waste) <&1
+	      (trap "stty `stty -g`; exit 0" 2 0; stty -icanon min 0 time 50; read waste) <&1
 	    fi
 	fi
 	if [ "$ISA64" = "1" -a "$KERNEL_BITS" = "64" ]; then
@@ -552,7 +552,7 @@
 	    echo "         invoke '$THERE/Configure linux-ppc64' *manually*."
 	    if [ "$TEST" = "false" -a -t 1 ]; then
 		echo "         You have about 5 seconds to press Ctrl-C to abort."
-		(trap "stty `stty -g`" 2 0; stty -icanon min 0 time 50; read waste) <&1
+		(trap "stty `stty -g`; exit 0" 2 0; stty -icanon min 0 time 50; read waste) <&1
 	    fi
 	fi
 	if [ "$KERNEL_BITS" = "64" ]; then
@@ -569,7 +569,7 @@
 	echo "         invoke '$THERE/Configure linux64-mips64' *manually*."
 	if [ "$TEST" = "false" -a -t 1 ]; then
 	    echo "         You have about 5 seconds to press Ctrl-C to abort."
-	    (trap "stty `stty -g`" 2 0; stty -icanon min 0 time 50; read waste) <&1
+	    (trap "stty `stty -g`; exit 0" 2 0; stty -icanon min 0 time 50; read waste) <&1
 	fi
 	OUT="linux-mips64"
 	;;
@@ -586,7 +586,7 @@
 	echo "         invoke '$THERE/Configure linux64-sparcv9' *manually*."
 	if [ "$TEST" = "false" -a -t 1 ]; then
 	  echo "          You have about 5 seconds to press Ctrl-C to abort."
-	  (trap "stty `stty -g`" 2 0; stty -icanon min 0 time 50; read waste) <&1
+	  (trap "stty `stty -g`; exit 0" 2 0; stty -icanon min 0 time 50; read waste) <&1
 	fi
 	OUT="linux-sparcv9" ;;
   sparc-*-linux2)
@@ -634,7 +634,7 @@
 	#  echo "         have to invoke './Configure linux32-s390x' *manually*."
 	#  if [ "$TEST" = "false" -a -t -1 ]; then
 	#    echo "         You have about 5 seconds to press Ctrl-C to abort."
-	#    (trap "stty `stty -g`" 2 0; stty -icanon min 0 time 50; read waste) <&1
+	#    (trap "stty `stty -g`; exit 0" 2 0; stty -icanon min 0 time 50; read waste) <&1
 	#  fi
 	#fi
 	OUT="linux64-s390x"
@@ -663,7 +663,7 @@
 		echo "         invoke '$THERE/Configure solaris64-sparcv9-cc' *manually*."
 		if [ "$TEST" = "false" -a -t 1 ]; then
 		  echo "         You have about 5 seconds to press Ctrl-C to abort."
-		  (trap "stty `stty -g`" 2 0; stty -icanon min 0 time 50; read waste) <&1
+		  (trap "stty `stty -g`; exit 0" 2 0; stty -icanon min 0 time 50; read waste) <&1
 		fi
 	    elif [ "$CC" = "gcc" -a "$GCC_ARCH" = "-m64" ]; then
 		# $GCC_ARCH denotes default ABI chosen by compiler driver
@@ -675,7 +675,7 @@
 		echo "         invoke '$THERE/Configure solaris-sparcv9-gcc' *manually*."
 		if [ "$TEST" = "false" -a -t 1 ]; then
 		  echo "         You have about 5 seconds to press Ctrl-C to abort."
-		  (trap "stty `stty -g`" 2 0; stty -icanon min 0 time 50; read waste) <&1
+		  (trap "stty `stty -g`; exit 0" 2 0; stty -icanon min 0 time 50; read waste) <&1
 		fi
 	    elif [ "$GCC_ARCH" = "-m32" ]; then
 		echo "NOTICE! If you *know* that your GNU C supports 64-bit/V9 ABI"
@@ -683,7 +683,7 @@
 		echo "        invoke '$THERE/Configure solaris64-sparcv9-gcc' *manually*."
 		if [ "$TEST" = "false" -a -t 1 ]; then
 		  echo "         You have about 5 seconds to press Ctrl-C to abort."
-		  (trap "stty `stty -g`" 2 0; stty -icanon min 0 time 50; read waste) <&1
+		  (trap "stty `stty -g`; exit 0" 2 0; stty -icanon min 0 time 50; read waste) <&1
 		fi
 	    fi
 	fi
@@ -764,7 +764,7 @@
 		echo "         invoke '$THERE/Configure hpux64-parisc2-cc' *manually*."
 		if [ "$TEST" = "false" -a -t 1 ]; then
 		  echo "         You have about 5 seconds to press Ctrl-C to abort."
-		  (trap "stty `stty -g`" 2 0; stty -icanon min 0 time 50; read waste) <&1
+		  (trap "stty `stty -g`; exit 0" 2 0; stty -icanon min 0 time 50; read waste) <&1
 		fi
 	     fi
 	elif [ $CPU_VERSION -ge 528 ]; then	# PA-RISC 1.1+ CPU
@@ -796,7 +796,7 @@
 		echo "         invoke '$THERE/Configure aix64-cc' *manually*."
 		if [ "$TEST" = "false" -a -t 1 ]; then
 		    echo "         You have ~5 seconds to press Ctrl-C to abort."
-		    (trap "stty `stty -g`" 2 0; stty -icanon min 0 time 50; read waste) <&1
+		    (trap "stty `stty -g`; exit 0" 2 0; stty -icanon min 0 time 50; read waste) <&1
 		fi
 	    fi
 	fi