We flag illegal pragma Elaborate with a call to Error_Msg on the pragma
argument, which in turn calls Set_Error_Posted on the enclosing
statement, i.e. on the pragma itself. The explicit call to
Set_Error_Posted on the pragma itself was redundant.

Cleanup related to handling of illegal code when detecting uninitialized
scalar objects.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* sem_prag.adb (Analyze_Pragma): Remove redundant call to
	Set_Error_Posted.