msginit: Fix invocation of helper programs on Windows.
Reported by Michele Locati <michele@locati.it>
in <https://lists.gnu.org/archive/html/bug-gettext/2019-04/msg00058.html>.
* autogen.sh (GNULIB_MODULES_TOOLS_FOR_SRC): Add configmake.
* gettext-tools/src/msginit.c: Include configmake.h.
(main): Add BINDIR to the PATH.
