ada: Reject pragma Attach_Handler on procedures in protected bodies

Pragma Attach_Handler and Interrupt_Handler are only legal for procedures
declared in protected definition. When given for procedures declared in
protected body, they were wrongly accepted and triggered an odd error message
from expansion.

gcc/ada/ChangeLog:

	* sem_prag.adb (Check_Interrupt_Or_Attach_Handler): Refine test for
	protected procedures; fix typo in comment.