exp_dist.adb (Build_From_Any_Call, [...]): For a used-defined subtype, always go to the first subtype of the base type.

2012-12-05  Thomas Quinot  <quinot@adacore.com>

	* exp_dist.adb (Build_From_Any_Call, Build_To_Any_Call,
	Build_TypeCode_Call): For a used-defined subtype, always go to
	the first subtype of the base type.

From-SVN: r194206