[Ada] Incorrect ineffective use type clause warning

[Ada] Incorrect ineffective use type clause warning

This patch fixes an issue in the compiler whereby a use_type_clause
incorrectly gets flagged as ineffective when the use of it comes after a
generic package instantiation where the installation of private use
clauses are required and one such clause references the same type.

gcc/ada/

	* sem_ch8.adb (Use_One_Type): Remove code in charge of setting
	Current_Use_Clause when Id is known to be redundant, and modify
	the printing of errors associated with redundant use type
	clauses so that line number gets included in more cases.