[Fortran, Patch] Implement IMPLICIT NONE

[Tobias Burnus]

FX wrote:
>>> Build and regtested on x86-64-gnu-linux.
>>> OK for the trunk?
> Looks mostly OK, but I have one question: I don’t understand what the wording "Type IMPLICIT NONE statement” is supposed to mean. Why “type”?

Well, I want to distinguish "IMPLICIT NONE (external)" which only 
applies to procedures from "IMPLICIT NONE" alias "IMPLICIT NONE (type)" 
which applies only to variables and function (return value) types. Thus,
   IMPLICIT NONE (external)
   IMPLICIT integer(a-z)
is valid while
   IMPLICIT NONE
   IMPLICIT integer(a-z)
is not.

If you have a better suggestion for the wording …

Tobias