gpg: Use gpgrt's new option parser to provide a global conf file.

* common/util.h: Remove argparse.h.
* common/argparse.c: Undef GPGRT_ENABLE_ARGPARSE_MACROS.
* configure.ac (GPGRT_ENABLE_ARGPARSE_MACROS): Define.
* agent/gpg-agent.c: Undef GPGRT_ENABLE_ARGPARSE_MACROS and include
argparse.h.  Do this also for all main modules which use our option
parser except for gpg.  Replace calls to strusage by calls to
gpgrt_strusage everywhere.

* g10/gpg.c (opts): Change type to gpgrt_opt_t.  Flag oOptions and
oNoOptions with ARGPARSE_conffile and ARGPARSE_no_conffile.
(main): Change type of pargs to gpgrt_argparse_t.  Rework the option
parser to make use of the new gpgrt_argparser.
--

This is not yet finished but a make check works.  gpg has the most
complex and oldest option handling and thus this is the first
migration target.  SE-Linux checks and version-ed config files are
missing and will be added later.

GnuPG-bug-id: 4788
Signed-off-by: Werner Koch <wk@gnupg.org>

configure.ac

@@ -522,7 +522,7 @@ AH_BOTTOM([
 #define GNUPG_CACHE_DIR         "cache.d"
 
 #define GNUPG_DEF_COPYRIGHT_LINE \
-        "Copyright (C) 2018 Free Software Foundation, Inc."
+        "Copyright (C) 2020 Free Software Foundation, Inc."
 
 /* For some systems (DOS currently), we hardcode the path here.  For
    POSIX systems the values are constructed by the Makefiles, so that
@@ -580,6 +580,9 @@ AH_BOTTOM([
 /* Enable the log_ macros from gpgrt.  */
 #define GPGRT_ENABLE_LOG_MACROS 1
 
+/* We want the argparse macros from gpgrt.  */
+#define GPGRT_ENABLE_ARGPARSE_MACROS 1
+
 /* Tell libgcrypt not to use its own libgpg-error implementation. */
 #define USE_LIBGPG_ERROR 1