move utf, fmt to libc

include/libc.h

@@ -9,6 +9,9 @@
 extern "C" {
 #endif                                                                
 
+#include <utf.h>
+#include <fmt.h>
+
 /*
  * Begin usual libc.h 
  */

include/u.h

@@ -33,8 +33,6 @@ extern "C" {
 #include <assert.h>
 #include <setjmp.h>
 #include <stddef.h>
-#include <utf.h>
-#include <fmt.h>
 #include <math.h>
 #include <ctype.h>	/* for tolower */