* sem_ch6.adb (Analyze_Subprogram_Declaration): Do not set the
Corresponding_Body on a defaulted null formal subprogram.
* sem_ch12.adb (Check_Formal_Package_Instance): No check needed
on a defaulted formal subprogram that is a null procedure.
* exp_ch9.adb: Update the comments involving pragma Implemented.
* sem_ch3.adb (Check_Pragma_Implemented (Entity_Id)): Add local
constant Subp_Alias and local variable Impl_Subp. Properly
handle aliases of synchronized wrappers. Code cleanup.
(Check_Pragma_Implemented (Entity_Id; Entity_Id)): Add
Name_Optional as part of the condition.
* sem_prag.adb (Analyze_Pragma): Add "Optional" as one of the
valid choices of implementation kind.
(Check_Arg_Is_One_Of): New routine.
* snames.ads-tmlp: Add Name_Optional.
2012-01-23 Ed Schonberg <schonberg@adacore.com>
* par-ch13.adb: Better error recovery in illegal aspect
specification.