Fix the document of keep_fnames option

README.md

@@ -378,8 +378,9 @@ to set `true`; it's effectively a shortcut for `foo=true`).
   for code which relies on `Function.length`.
 
 - `keep_fnames` -- default `false`.  Pass `true` to prevent the
-  compressor from mangling/discarding function names.  Useful for code relying on
-  `Function.prototype.name`.
+  compressor from discarding function names.  Useful for code relying on
+  `Function.prototype.name`. You may also would like to refer to
+  [the mangle option](#mangle).
 
 - `passes` -- default `1`. Number of times to run compress. Use an
   integer argument larger than 1 to further reduce code size in some cases.
@@ -696,6 +697,9 @@ Other options:
   - `eval` — mangle names visible in scopes where eval or with are used
   (disabled by default).
 
+- `keep_fnames` -- default `false`.  Pass `true` when you'd not like to mangle
+  function names.  Useful for code relying on `Function.prototype.name`.
+
   Examples:
 
   ```javascript