[Ada] Improve message for condition always False (simple variable case)

[Arnaud Charlet <charlet at adacore dot com>]

The warning message for an always True condition special cased the
simple variable case. This special casing is now extended for the
False case as well:

     1. package CCF_Warn is
     2.    procedure Mess;
     3. end;

     1. package body CCF_Warn is
     2.     type T is array (1..10) of Integer;
     3.     Thing : T := (others => 111);
     4.
     5.     procedure Change (X : integer; Y : out Boolean) is
     6.     begin
     7.         Y := X > 17;
     8.     end Change;
     9.
    10.    procedure Mess is
    11.     Blinking   : Boolean;
    12.     Some_Blink : Boolean;
    13.    begin
    14.
    15.      Blinking := False;
    16.      Some_Blink := False;
    17.
    18.      if Thing (3) = Thing (5) then
    19.         Change (10, Some_Blink);
    20.
    21.         Blinking := Blinking or Some_Blink;
                            |
        >>> warning: object "Blinking" is always False
        >>> warning: (see assignment at line 15)

    22.
    23.      else
    24.         for X in T'range loop
    25.           Thing (X) := -1;
    26.         end loop;
    27.      end if;
    28.    end;
    29. end;

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

2015-01-30  Robert Dewar  <dewar@adacore.com>

	* sem_warn.adb (Warn_On_Known_Condition): Do special casing of
	message for False case.

Attachment: difs
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