Document INI_HANDLER_LINENO compile-time option

README.md

@@ -15,6 +15,7 @@ Download a release, browse the source, or read about [how to use inih in a DRY s
   * **Stack vs heap:** By default, inih allocates its line buffer on the stack. To allocate on the heap using `malloc` instead, specify `-DINI_USE_STACK=0`.
   * **Stop on first error:** By default, inih keeps parsing the rest of the file after an error. To stop parsing on the first error, add `-DINI_STOP_ON_FIRST_ERROR=1`.
   * **Maximum line length:** The default maximum line length is 200 bytes. To override this, add something like `-DINI_MAX_LINE=1000`.
+  * **Report line numbers:** By default, the `ini_handler` callback doesn't receive the line number as a parameter. If you need that, add `-DINI_HANDLER_LINENO=1`.
 
 
 ## Simple example in C ##