* gdbint.texinfo (Algorithms): Add new section describing the

    * gdbint.texinfo (Algorithms): Add new section describing the
        Observer paradigm.
        (Top): Add menu entry to new observer appendix.
        * observer.texi: New file.
        * Makefile.in (GDBINT_DOC_SOURCE_INCLUDES): Add dependency on
        new observer.texi file.