card-tool: Add skeleton for new tool

* tools/gpg-card-tool.c: New.
* tools/gpg-card-tool-w32info.rc: New.
* tools/Makefile.am: Add new tool.

To support more cards than the OpenPGP card it is useful to have a
separate tool. It will have have the "gpg --card-edit" style
interactive interface as well as direct command line options for all
commands. In a first step the OpenPGP card will be supported, to
allow its use as an alternative to the gpg command, and the
forthcoming PIV card support.

The tool can be though as a direct interface to scdaemon.

• Signed-off-by: Werner Koch <wk@gnupg.org>