* sem_util.adb (Build_Explicit_Dereference): Set properly
the type of the prefix prior to rewriting, because subsequent
legality checks examine the original node.
* aspects.adb: Add Contract_Cases to the canonical aspects map.
* aspects.ads: Add aspect Contract_Cases in the various aspect
tables.
* par-prag.adb: The parser does not need to perform special
actions for pragma Contract_Cases.
* sem_ch6.adb (Expand_Contract_Cases): New routine.
(Process_Contract_Cases): Convert pragma Contract_Cases into pre-
and post- condition checks that verify the runtime state of all
case guards and their corresponding consequences.
* sem_ch13.adb (Analyze_Aspect_Specifications): Perform
various legality checks on aspect Contract_Cases. The aspect is
transformed into a pragma.
* sem_prag.adb: Add an entry in table Sig_Flags for pragma
Contract_Cases.
(Analyze_Pragma): Perform various legality
checks on pragma Contract_Cases. The pragma is associated with
the contract of the related subprogram.
(Chain_CTC): Omit pragma
Contract_Cases because it does not introduce a unique case name
and does not follow the syntax of Contract_Case and Test_Case.
* snames.ads-tmpl: Add new name Name_Contract_Cases. Add a
Pragma_Id for Contract_Cases.