add AbstractIrrational docs to manual

stevengj · stevengj · commit 9309e2e5fe7c · 2017-10-23T13:08:38.000-04:00
diff --git a/doc/src/stdlib/numbers.md b/doc/src/stdlib/numbers.md
@@ -11,6 +11,7 @@ Core.AbstractFloat
 Core.Integer
 Core.Signed
 Core.Unsigned
+Core.AbstractIrrational
 ```
 
 ### Concrete number types
