sync updated drw code from dmenu

important:
- drw_rect: didn't use w and h, change the dwm code accordingly.
- drw_text: text is NULL is not allowed, use drw_rect().

util.c

@@ -2,16 +2,32 @@
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "util.h"
 
-void
-die(const char *errstr, ...) {
-	va_list ap;
+void *
+ecalloc(size_t nmemb, size_t size)
+{
+	void *p;
 
-	va_start(ap, errstr);
-	vfprintf(stderr, errstr, ap);
-	va_end(ap);
-	exit(EXIT_FAILURE);
+	if (!(p = calloc(nmemb, size)))
+		perror(NULL);
+	return p;
 }
 
+void
+die(const char *fmt, ...) {
+	va_list ap;
+
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+
+	if (fmt[0] && fmt[strlen(fmt)-1] == ':') {
+		fputc(' ', stderr);
+		perror(NULL);
+	}
+
+	exit(1);
+}