Array equality is typically expanded into a loop, but for small arrays
such loops are inefficient (and the code generator might fail to turn
them into linear code, especially when the array contains records).

We optimize equality of 2-element arrays into an AND THEN expression,
but only for array types whose bounds are given by a range expression.
Now we do this for all 2-element arrays with compile-time known bounds,
regardless of how their bounds are given, e.g. for array types declared
like:

   type A1 is array (Integer range 1 .. 2) of ...;
   type A2 is array (Boolean) of ...;

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

gcc/ada/

	* exp_ch4.adb (Expand_Array_Equality): Remove check of the array
	bound being an N_Range node; use Type_High_Bound/Type_Low_Bound,
	which handle all kinds of array bounds.