gnat_rm.texi, [...]: Update doc.

gnat_rm.texi, [...]: Update doc.

        * gnat_rm.texi, gnat_ugn.texi,
        doc/gnat_ugn/gnat_project_manager.rst,
        doc/gnat_ugn/building_executable_programs_with_gnat.rst,
        doc/gnat_ugn/gnat_and_program_execution.rst,
        doc/gnat_ugn/gnat_utility_programs.rst,
        doc/gnat_ugn/the_gnat_compilation_model.rst,
        doc/gnat_rm/implementation_defined_attributes.rst,
        doc/gnat_rm/standard_and_implementation_defined_restrictions.rst,
        doc/gnat_rm/implementation_defined_pragmas.rst,
        doc/gnat_rm/the_gnat_library.rst,
        doc/gnat_rm/implementation_defined_aspects.rst: Update doc.
        * doc/Makefile: Cleanups.

From-SVN: r235328