(trivial) (ddoc) more descriptive Typedef doc.

Based on Andrei Alexandrescu's post: http://forum.dlang.org/post/lvj17a$78k$1@digitalmars.com

`MoneyEuros` makes use of the cookie more obvious than `TypeFloat1`.
Merge pull request #2543 from kiith-sa/patch-1

(trivial) (ddoc) more descriptive Typedef doc.