Add a @Deprecated annotation

[cglacet]

I think it would be a nice addition to have a @Deprecated annotation.

Maybe something like this:

;| @Global
  The function F computes 2x
  @Deprecated
  @Param x \<int\> : how it changed
  @Return \<int\> double of x
|;
(defun f (x)
  (* x 2)
)

Which would generate something like:

I generated this image using the following code, but it's a bit unstable (the @Deprecated should be on its own line, otherwise it will "eat" the description):

;| @Global
  @**Deprecated**
  The function F computes 2x
  @Param x \<int\> : how it changed
  @Return \<int\> double of x
|;
(defun f (x)
  (* x 2)
)

Maybe it would also be nice to have a deprecation message ? Like @Deprecated what to use instead.