* bindgen.adb Comment reformatting. Update the list of run-time globals.
	(Gen_Adainit_Ada): Add the declaration, import and value set for
	configuration flag Canonical_Streams.
	(Gen_Adainit_C): Add the declaration and initial value of external
	symbol __gl_canonical_streams.
	
	* init.c: Update the list of global values computed by the binder.
	
	* opt.ads: Add flag Canonical_Streams.
	
	* par-prag.adb (Prag): Include Pragma_Canonical_Streams to the list of
	semantically handled pragmas.
	
	* sem_prag.adb: Add an entry into enumeration type Sig_Flags.
	(Analyze_Pragma): Add case for pragma Canonical_Streams.
	
	* snames.adb: Add character value for name Canonical_Streams.
	
	* snames.ads:
	Add Name_Canonical_Streams to the list of configuration pragmas.
	Add Pragma_Canonical_Streams to enumeration type Pragma_Id.
	
	* snames.h: Add a definition for Pragma_Canonical_Streams.
	
	* s-ststop.adb:
	Add a flag and import to seize the value of external symbol
	__gl_canonical_streams. Update comment and initial value of constant
	Use_Block_IO.
	
	* gnat_rm.texi: Add section of pragma Canonical_Streams.
	
	* gnat_ugn.texi:
	Add pragma Canonical_Streams to the list of configuration pragmas.

From-SVN: r138407