m4: bump ax_pkg_swig to 15

m4: bump ax_pkg_swig to 15

If you happen to install the mingw-w64-x86_64-swig package on mingw64,
instead of just swig (the msys package), the swig lib is:

    $ /mingw64/bin/swig -swiglib
    C:\msys64\mingw64\bin\Lib
    C:/msys64/mingw64/share/swig/4.1.1

rather than:

    $ /usr/bin/swig -swiglib
    /usr/share/swig/4.0.2

The two lines are printed with a \r\n between them, which is not handled
well by the current AX_PKG_SWIG macro.  This results in this in
Makefiles:

    SWIG_LIB = C:\msys64\mingw64\bin\Lib
    C:/msys64/mingw64/share/swig/4.1.1

and these errors at the end of configure:

    config.status:1764: $? = 2
    config.status:1759: cd tests/param-validation       && sed -e '/# am--include-marker/d' Makefile         | make -f - am--depfiles
    /tmp/GmbY8tiu:351: *** missing separator.  Stop.
    config.status:1764: $? = 2
    config.status:1759: cd tests/plugins/src.ctf.fs/succeed       && sed -e '/# am--include-marker/d' Makefile         | make -f - am--depfiles
    /tmp/Gmg5rHoG:346: *** missing separator.  Stop.
    config.status:1764: $? = 2
    config.status:1759: cd tests/plugins/sink.ctf.fs/succeed       && sed -e '/# am--include-marker/d' Makefile         | make -f - am--depfiles
    /tmp/GmxjJjqn:350: *** missing separator.  Stop.
    config.status:1764: $? = 2
    config.status:1759: cd tests/plugins/flt.lttng-utils.debug-info       && sed -e '/# am--include-marker/d' Makefile         | make -f - am--depfiles
    /tmp/GmA652OJ:370: *** missing separator.  Stop.
    config.status:1764: $? = 2
    config.status:1759: cd tests/utils       && sed -e '/# am--include-marker/d' Makefile         | make -f - am--depfiles
    /tmp/GmzIx4FT:388: *** missing separator.  Stop.
    config.status:1764: $? = 2
    config.status:1759: cd tests/utils/tap       && sed -e '/# am--include-marker/d' Makefile         | make -f - am--depfiles
    /tmp/GmtBtVgx:347: *** missing separator.  Stop.
    config.status:1764: $? = 2
    config.status:1768: error: in `/c/cygwin64/home/Baube/src/babeltrace':
    config.status:1770: error: Something went wrong bootstrapping makefile fragments
        for automatic dependency tracking.  If GNU make was not used, consider
        re-running the configure script with MAKE="gmake" (or whatever is
        necessary).  You can also try re-running configure with the
        '--disable-dependency-tracking' option to at least be able to build
        the package (albeit without support for automatic dependency tracking).
    See `config.log' for more details

It was fixed here:

  https://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=commit;h=1168996c4cbf6d529d90f66bbf6b06e412bc4452

Import the latest version of the file as of today.

Change-Id: I19cdbdcca4fb3bd5a4ba3b54fbf3a29c2f4fc53f
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/9583
Reviewed-by: Michael Jeanson <mjeanson@efficios.com>
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>