[Ada] Fix alignment issue on array subtypes

[Arnaud Charlet <charlet at adacore dot com>]

Tested on i686-linux, committed on mainline.

Gigi does not propagate the alignment on array subtypes, whereas it does on
(unconstrained) array types.  But it makes a padding record around the array
subtype if it deems it necessary in order to bump the alignment.
The problem occurs at subprogram boundaries: when the type is passed by
reference because of the ABI, the padding type may be stripped so we may end
up with a parameter of a reference type to the original, non-promoted type;
when known_alignment is invoked on this parameter, it thus returns the
default alignment.
The fix is to treat parameters passed by reference by default like parameters
passed by reference by virtue of their type.

2005-07-07  Eric Botcazou  <ebotcazou@adacore.com>

	* decl.c (gnat_to_gnu_entity) <E_Procedure>: Do not strip the padding
	type if the parameter is not passed by copy but reference by default.

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