* doc/gnat_ugn/building_executable_programs_with_gnat.rst,
	doc/gnat_ugn/gnat_utility_programs.rst
	doc/gnat_rm/implementation_defined_attributes.rst
	doc/gnat_rm/implementation_defined_pragmas.rst
	doc/gnat_rm/representation_clauses_and_pragmas.rst
	doc/gnat_rm/about_this_guide.rst
	doc/gnat_rm/implementation_of_ada_2012_features.rst: Doc improvements.
	* gnat_rm.texi, gnat_ugn.texi: Regenerate.

From-SVN: r221628