Expose MySQL affected row counts

site/doc/areas/mysql.txt

@@ -5,4 +5,5 @@ mysql_disconnect
 mysql_error
 mysql_escape
 mysql_insert_id
+mysql_affected_rows
 mysql_query

site/doc/pages/mysql_affected_rows.txt

@@ -0,0 +1,24 @@
+:sig
+u32 mysql_affected_rows(MySQL* m)
+
+:params
+m : pointer to an active MySQL connection
+return value : number of rows changed by the most recent statement
+
+:see
+>mysql
+mysql_query
+mysql_insert_id
+
+:content
+Returns the number of rows changed by the most recent insert, update, or delete on the connection. A successful statement that returns rows, a rejected query, or a null connection returns `0` rather than retaining an earlier statement's count.
+
+:example
+MySQL* db = mysql_connect();
+if(db != 0)
+{
+    mysql_query(db, "update users set active=1 where active=0");
+    print("rows updated: ", mysql_affected_rows(db), "\n");
+    mysql_disconnect(db);
+}
+else print("(requires a reachable MySQL server)\n");

site/doc/pages/mysql_query.txt

@@ -9,6 +9,7 @@ return value : a list of rows returned from executing the query
 
 :see
 >mysql
+mysql_affected_rows
 
 :content
 Executes a MySQL query and returns the resulting data, if any.
@@ -17,6 +18,8 @@ Executes a MySQL query and returns the resulting data, if any.
 
 The result is returned as a `DValue`, which makes it easy to iterate through rows and read fields with the usual `DValue` accessors.
 
+After an insert, update, or delete, use `mysql_affected_rows()` to inspect how many rows changed.
+
 :example
 MySQL* db = mysql_connect();
 if(db != 0)