fix linking to the python library (use -L$PYLIBDIR -lpython$pyver)

as far as i saw the reason to use an absolute path for linking instead
of using -lpythonX.XX is that at least debian does not ship a shared
object within the basic python3 package so you have to install the -dev
package (that's kinda weird^H^H^H^H^Hf***ed up).

configure.in

@@ -4120,9 +4120,9 @@ elif test -n "$with_system_python" -o -n "$with_system_libs" && \
    python_include=`$PYTHON -c "import distutils.sysconfig; print(distutils.sysconfig.get_config_var('INCLUDEPY'));"`
    python_version=`$PYTHON -c "import distutils.sysconfig; print(distutils.sysconfig.get_config_var('VERSION'));"`
    python_libs=`$PYTHON -c "import distutils.sysconfig; print(distutils.sysconfig.get_config_var('LIBS'));"`
-   python_ldlib=`$PYTHON -c "import distutils.sysconfig; print(distutils.sysconfig.get_config_var('LIBDIR') + '/' + distutils.sysconfig.get_config_var('LDLIBRARY'));"`
+   python_libdir=`$PYTHON -c "import distutils.sysconfig; print(distutils.sysconfig.get_config_var('LIBDIR'));"`
    PYTHON_CFLAGS="-I$python_include"
-   PYTHON_LIBS="$python_ldlib $python_libs"
+   PYTHON_LIBS="-L$python_libdir -lpython$python_version $python_libs"
 fi
 if test "$with_system_python" = "yes" ; then
    SYSTEM_PYTHON=YES