MINOR: tools: increase the number of ITOA strings to 16

It's currently 10 and is too little to extend some tooltips on the stats page.
diff --git a/include/common/standard.h b/include/common/standard.h
index a3e8275..dc77147 100644
--- a/include/common/standard.h
+++ b/include/common/standard.h
@@ -57,7 +57,7 @@
 #define NB_LLMAX_STR (sizeof("-9223372036854775807")-1)
 
 /* number of itoa_str entries */
-#define NB_ITOA_STR	10
+#define NB_ITOA_STR	16
 
 /* maximum quoted string length (truncated above) */
 #define QSTR_SIZE 200