libyang MAINTENANCE change format of the empty loops

To improve readability and because of processing by the formatting
tools, add explicit empty block to the empty loops (for, while).
diff --git a/compat/compat.c b/compat/compat.c
index c056484..7a06d58 100644
--- a/compat/compat.c
+++ b/compat/compat.c
@@ -80,7 +80,7 @@
     size_t len = 0;
 
     /* strnlen */
-    for (; (len < n) && (s[len] != '\0'); ++len);
+    for (; (len < n) && (s[len] != '\0'); ++len) {}
 
     if (!(buf = malloc(len + 1U))) {
         return NULL;