* generic/gdbtk-cmds.c: Don't include itcl.h.

    * generic/gdbtk-cmds.c: Don't include itcl.h.
        * generic/gdbtk-hooks.c: Likewise.
        * generic/gdbtk.c: Include tcl.h and tk.h instead of itcl.h
        and itk.h.
        (gdbtk_init): Rewrite to accommodate using a system-provided
        Tcl, Tk, Itcl, Itk.
        (gdbtk_source_start_file) [!_WIN32]: Don't call error() when
        we fail to source the start file. Just dump the message to stderr.
        Throw an exception indicating the failure.
        * library/ehandler.itb (GDBEventHander::dispatch): "itcl_info" is
        deprecated: use "itcl::find objects" instead.
        * library/managedwin.itb (window_instance): Ditto.
        (restart): Ditto.
        (shutdown): Ditto.
        (_open): Ditto.
        (find): Ditto.
        * library/globalpref.itb (_build_win): Don't pass config arguments
        for libgui widgets to the constructor. Configure the widget after
        creation.
        * library/srcpref.itb (_build_win): Ditto.
        * library/main.tcl: Update Tcl, Tk, Itcl, Itk, and Iwidgets (just
        added to this loop) version requirements.
        No need to initialize Iwidgets separately.
        * plugins/Make-rules (TCLHDIR): Renamed to TCL_INCLUDES. Change
        all references.
        (TCL_BUILD_LIB_SPEC): Renamed to TCL_LIBRARY. Change all references.
        * plugins/acinclude.m4: Include the standard tcl.m4 instead
        of the sourceware-derived one.
        * plugins/configure.ac: Use Tcl's standard SC_* macros instead of
        the sourceware-derived CYG_AC_* macros.
        Add logic to deal with using a system-supplied Tcl/Tk.
        * plugins/configure: Regenerated.
        * plugins/Makefile.in: Regenerated.