apply xclearwin patch

st.c

@@ -2189,10 +2189,8 @@ strhandle(void)
 				fprintf(stderr, "erresc: invalid color j=%d, p=%s\n",
 				        j, p ? p : "(null)");
 			} else {
-				/*
-				 * TODO if defaultbg color is changed, borders
-				 * are dirty
-				 */
+				if (j == defaultbg)
+					xclearwin();
 				tfulldirt();
 			}
 			return;

win.h

@@ -39,3 +39,4 @@ void xsetpointermotion(int);
 void xsetsel(char *);
 int xstartdraw(void);
 void xximspot(int, int);
+void xclearwin(void);

x.c

@@ -862,6 +862,12 @@ xclear(int x1, int y1, int x2, int y2)
 			x1, y1, x2-x1, y2-y1);
 }
 
+void
+xclearwin(void)
+{
+	xclear(0, 0, win.w, win.h);
+}
+
 void
 xhints(void)
 {