rtsfind.ads: Add block IO versions of stream routines for Strings.

rtsfind.ads: Add block IO versions of stream routines for Strings.

2008-08-01  Hristian Kirtchev  <kirtchev@adacore.com>

	* rtsfind.ads: Add block IO versions of stream routines for Strings.

	* bindgen.adb, gnat_rm.texi, gnat_ugn.texi, opt.ads,
	sem_prag.adb, snames.adb, snames.ads, snames.h,
	par-prag.adb: Undo Canonical_Streams related changes.

	* s-rident.ads: Add new restriction No_Stream_Optimizations.

	* s-ststop.ads, s-ststop.adb: Comment reformatting.
	Define enumeration type to designate different IO mechanisms.
	Enchance generic package Stream_Ops_Internal to include an
	implementation of Input and Output.

	* exp_attr.adb (Find_Stream_Subprogram): If restriction
	No_Stream_Optimization is active, choose the default byte IO
	implementations of stream attributes for Strings.
	Otherwise use the corresponding block IO version.

From-SVN: r138511