lib-load.adb (Load_Unit): Skip the test for a unit not found when its file has already been loaded...

2006-10-31  Vincent Celier  <celier@adacore.com>

	* lib-load.adb (Load_Unit): Skip the test for a unit not found when
	its file has already been loaded, according to the unit being loaded,
	not to the current value of Multiple_Unit_Index.

From-SVN: r118284