[BUILD] warning ultoa_r returns char *

ultoa_r modifies its output, it returns a char *.
diff --git a/src/standard.c b/src/standard.c
index aab318b..6ae4dd7 100644
--- a/src/standard.c
+++ b/src/standard.c
@@ -57,7 +57,7 @@
  * This function simply returns a locally allocated string containing
  * the ascii representation for number 'n' in decimal.
  */
-const char *ultoa_r(unsigned long n, char *buffer, int size)
+char *ultoa_r(unsigned long n, char *buffer, int size)
 {
 	char *pos;