[Ada] Remove special handling for package declaring abstract state

[Arnaud Charlet <charlet at adacore dot com>]

On the basis of further discussion, we decided not to implement the
rule saying that a package body must be required for some other
reason if an abstract state is declared. Now we just say a package
body is required if a non-null abstract state and that's it! This
change undoes the error message. So if we compile the following
with -gnatd.V -gnatld7 (but without -gnatc), we get

cannot generate code for file nnas.ads (package spec)

Compiling: nnas.ads

     1. package NNAS
     2.    with Abstract_State => State
     3. is
     4.    --  package declarations with non-null
     5.    --  Abstract State shall have bodies.
     6. end NNAS;

 6 lines: No errors

The "cannot generate" line reflects the fact that this package
spec requires a body, so the spec cannot be compiled alone.

Tested on x86_64-pc-linux-gnu, committed on trunk

2013-10-17  Robert Dewar  <dewar@adacore.com>

	* sem_ch7.adb (Analyze_Package_Specification): Remove circuit
	for ensuring that a package spec requires a body for some other
	reason than that it contains the declaration of an abstract state.

Attachment: difs
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