add PID file handling to clients (including signal handling to remove the files)

configure.in

@@ -273,6 +273,30 @@ dnl Select drivers to build
 LCD_DRIVERS_SELECT
 
 
+# directory for PID files
+pidfiledir=/var/run
+# make sure the directory exists
+if test ! -d $pidfiledir ; then
+        pidfiledir=`eval echo ${sysconfdir}`
+	case $pidfiledir in
+		NONE/*) pidfiledir=`echo $pidfiledir | sed "s~NONE~$ac_default_prefix~"` ;;
+	esac
+fi
+		
+AC_ARG_WITH(pidfile-dir,
+	[AS_HELP_STRING([--with-pidfile-dir=PATH], [specify location of pid files [/var/run]])],
+	[ if test -n "$withval"  &&  test "x$withval" != "xno"  &&  \
+	     test "x${withval}" != "xyes"; then
+		pidfiledir=$withval
+		if test ! -d $pidfiledir ; then
+			AC_MSG_WARN([** no $pidfiledir directory on this system **])
+		fi
+	fi ]
+)
+
+AC_SUBST(pidfiledir)
+
+
 # Features applicable to the server
 AC_ARG_ENABLE(seamless-hbars,
 	[AS_HELP_STRING([--enable-seamless-hbars], [no gaps in horizontal bar graphs (if HW supports it)])],