qdoc: Document macro parameters

QDoc has the ability to accept parameters for macros but it was
never documented.

Change-Id: Iaf9a629c906fbe1552717c7444a0fd52b5655a3f
Reviewed-by: Martin Smith <martin.smith@digia.com>

src/tools/qdoc/doc/qdoc-manual-qdocconf.qdoc

@@ -734,6 +734,18 @@
     command to render a superscript asterisk, but only when generating
     HTML.
 
+    A macro can also take up to seven parameters:
+
+    \badcode
+        macro.hello            = "Hello \1!"
+    \endcode
+
+    Parameters are passed to macros the same way as to other commands:
+
+    \badcode
+    \hello World
+    \endcode
+
     See also \l {alias-variable} {alias}.
 
     \target manifestmeta-variable