fix crash when x11 window is too small, and improve Xv detection in configure script

acinclude.m4

@@ -152,13 +152,16 @@ AC_DEFUN([MS_CHECK_VIDEO],[
 		  	  esac],[enable_xv=true])
 
 			if test "$enable_xv" = "true"; then
-			   AC_CHECK_HEADERS(X11/extensions/Xv.h,[] ,[enable_xv=false])
+				AC_CHECK_HEADERS(X11/extensions/Xv.h,[] ,[enable_xv=false])
+				AC_CHECK_HEADERS(X11/extensions/Xvlib.h,[] ,[enable_xv=false],[
+					#include <X11/Xlib.h>
+				])
 			   AC_CHECK_LIB(Xv,XvCreateImage,[LIBS="$LIBS -lXv"])
 			 fi
 		fi
 		
 		if ! test "$mingw_found" = "yes" ; then
-			if test "$enable_xv$sdl_found" == "nono" ; then
+			if test "$enable_xv$sdl_found" == "falsefalse" ; then
 				AC_MSG_ERROR([No video output API found. Install either X11+Xv headers or SDL library.])
 			fi
 		fi

src/layouts.h

@@ -26,6 +26,8 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 extern "C" {
 #endif
 
+#define MS_LAYOUT_MIN_SIZE 40
+
 void ms_layout_compute(MSVideoSize wsize, MSVideoSize vsize, MSVideoSize orig_psize,
                        int localrect_pos, float scalefactor, MSRect *mainrect, MSRect *localrect);
 

src/x11video.c

@@ -181,6 +181,10 @@ static void x11video_prepare(MSFilter *f){
 	}
 	XGetWindowAttributes(s->display,s->window_id,&wa);
 	ms_message("Window has size %i,%i",wa.width,wa.height);
+
+	if (wa.width<MS_LAYOUT_MIN_SIZE || wa.height<MS_LAYOUT_MIN_SIZE){
+		return;
+	}
 	
 	s->fbuf.w=wa.width & ~0x1;
 	s->fbuf.h=wa.height  & ~0x1;