[Ada] Warn for suspicious same range nested loops

[Arnaud Charlet <charlet at adacore dot com>]

If nested loops appear where the iteration ranges are over the
same range of a multi-dimensional range (where the range number
has been defaulted to 1), then a warning is issued as shown in
the following example:

     1. procedure Warn2D is
     2.    type E is array (Integer range <>, Integer range <>)
     3.      of Integer;
     4.    S : Integer := 0;
     5.    EE : E (1 .. 3, 1 .. 3) := (Others => (Others => 0));
     6. begin
     7.    for J in EE'Range loop
     8.       for K in EE'Range loop
                         |
        >>> warning: inner range same as outer range at line 7

     9.          S := S + EE (J, K);
    10.       end loop;
    11.    end loop;
    12. end Warn2D;

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

2012-10-29  Robert Dewar  <dewar@adacore.com>

	* sem_ch5.adb (Analyze_Loop_Statement): Add warning for identical
	inner/outer ranges.

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