* tcl.m4: Remove. I changed my mind.

    * tcl.m4: Remove. I changed my mind.
        * acinclude.m4: Include ../config/tcl.m4.
        (CY_AC_TCL_PRIVATE_HEADERS): New macro.
        (CY_AC_TK_PRIVATE_HEADERS): New macro.
        * configure.ac: When using in-tree tcl/tk, include
        Tcl's/Tk's platform directory.
        When using installed Tcl/Tk, use CY_AC_{TCL,TK}_PRIVATE_HEADERS
        to find the private header files.
        * aclocal.m4: Regenerated.
        * configure: Regenerated.
        * Makefile.in: Regenerated.
        * library/Makefile.in: Regenerated.
        * src/Makefile.in: Regenerated.