[Ada] fix wrong code for assignment from packed component

[Ralf Wildenhues]

Hello Olivier,

A miniscule typo nit:

* Olivier Hainque wrote on Mon, Mar 31, 2008 at 06:56:49PM CEST:
> *** ada/utils2.c	(revision 133345)
> --- ada/utils2.c	(working copy)
[...]
> !   /* We must prevent writing more than what the target may hold if this is for
> !      an assignment and the case of tagged types is handled in build_binary_op
> !      so use the lhs type if it is known to be smaller, or of constant size and
> !      the rhs type is not, whatever the modes.  We also force t1 in case of
> !      contant size equality to minimize occurrences of view conversions on the
> !      lhs of assignments.  */

s/contant/constant/

Cheers,
Ralf