yang printer BUGFIX order of the substatements in import statement

extension instances are supposed to be printed first
diff --git a/src/printer_yang.c b/src/printer_yang.c
index 98e2f86..c19ebdc 100755
--- a/src/printer_yang.c
+++ b/src/printer_yang.c
@@ -1703,10 +1703,10 @@
     for (i = 0; i < module->imp_size; i++) {
         ly_print(out, "\n%*simport %s {\n", LEVEL, INDENT, module->imp[i].module->name);
         level++;
-        yang_print_substmt(out, level, LYEXT_SUBSTMT_PREFIX, 0, module->imp[i].prefix,
-                           module, module->imp[i].ext, module->imp[i].ext_size);
         yang_print_extension_instances(out, level, module, LYEXT_SUBSTMT_SELF, 0,
                                        module->imp[i].ext, module->imp[i].ext_size);
+        yang_print_substmt(out, level, LYEXT_SUBSTMT_PREFIX, 0, module->imp[i].prefix,
+                           module, module->imp[i].ext, module->imp[i].ext_size);
         if (module->imp[i].rev[0]) {
             yang_print_substmt(out, level, LYEXT_SUBSTMT_REVISIONDATE, 0, module->imp[i].rev,
                                module, module->imp[i].ext, module->imp[i].ext_size);