gpg: Warn about (but don't fail) on scdaemon options in gpg.conf.

* g10/gpg.c: Add config options that should belong in scdaemon.conf
* g10/main.h, g10/misc.c (obsolete_scdaemon_option): New.

In gpg2, the following options are only relevant for scdaemon:

reader-port
ctapi-driver
pcsc-driver
disable-ccid

but in gpg1, they are options for gpg itself.

Some users of gpg1 might have these options in their
~/.gnupg/gpg.conf, which causes gpg2 to fail hard if it reads that
config file.

gpg2 should not fail hard, though giving a warning (and suggesting a
move to scdaemon.conf) seems OK.

This patch does *not* reintroduce any documentation for these options
in gpg.texi, even to indicate that they are "dummy" options, since
scdaemon.texi contains the appropriate documentation.

• Program names factored out from obsolete_scdaemon_option to make reuse without new translations easier. -wk

• Debian-bug-id: #762844