[Ada] Fix wrong number of iterations for specific loop

[Eric Botcazou]

This is a regression present on all the active branches.  The compiler 
generates code that doesn't execute the expected number of iterations for a 
loop with a dynamic upper bound whose value is exactly the upper bound of the 
base index type and is obtained through a narrowing conversion.

Tested on x86_64-suse-linux, applied on all the active branches.


2013-08-13  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/trans.c (can_equal_min_or_max_val_p): Be prepared for
	values outside of the range of the type.


2013-08-13  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/loop_optimization16.adb: New test.
	* gnat.dg/loop_optimization16_pkg.ad[sb]: New helper.


-- 
Eric Botcazou
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