D support: Add the runtime library.

D support: Add the runtime library.

* gnulib-local/m4/d.m4: New file.
* gnulib-local/modules/d: New file.
* gnulib-local/Makefile.am (EXTRA_DIST): Add d.m4 and the 'd' module.
* autogen.sh (GNULIB_MODULES_RUNTIME_OTHER): Add d, dcomp-script.
* gettext-runtime/intl-d/Makefile.am: New file.
* gettext-runtime/intl-d/gnu/libintl/package.d: New file.
* gettext-runtime/intl-d/gnu/libintl/libintl.d: New file.
* gettext-runtime/intl-d/gnu/libintl/internal/low.d: New file.
* gettext-runtime/configure.ac: Invoke gt_D_CHOICE, gt_DCOMP. Set the variable
BUILDD and the Automake conditional BUILD_D.
* gettext-runtime/Makefile.am (SUBDIRS): Add intl-d.
* NEWS: Mention libintl_d.a.
* gettext-runtime/NEWS: Likewise.
* PACKAGING: Add the sources and binary for the libintl_d library.
* DEPENDENCIES: Mention the D compiler and runtime.