Remove use of gnulib (part 1)

* gl/: Remove entire tree.
* configure.ac: Remove gnulib tests and the gl/ Makefile.
(setenv): Add to AC_CHECK_FUNCS.
* autogen.rc (extra_aclocal_flags): Set to empty.
* Makefile.am (ACLOCAL_AMFLAGS): Remove -I gl/m4
(SUBDIRS): Remove gl/.
* agent/Makefile.am (common_libs): Remove ../gl/gnulib.a
* common/Makefile.am (t_common_ldadd): Ditto.
* dirmngr/Makefile.am (dirmngr_LDADD): Ditto.
(dirmngr_ldap_LDADD, dirmngr_client_LDADD): Ditto.
* g10/Makefile.am (needed_libs): Ditto.
* g13/Makefile.am (g13_LDADD): Ditto.
* kbx/Makefile.am (kbxutil_LDADD): Ditto.
($(PROGRAMS)): Ditto.
* scd/Makefile.am (scdaemon_LDADD): Ditto.
* sm/Makefile.am (common_libs): Ditto.
* tools/Makefile.am (common_libs, commonpth_libs): Ditto.

* agent/gpg-agent.c: Remove "mkdtemp.h"
* g10/exec.c: Ditto.
* scd/scdaemon.c: Ditto.
* tools/symcryptrun.c: Ditto.
* common/sysutils.c: Remove "setenv.h"

* common/t-timestuff.c: Use putenv if setenv is not available.
--

gnulib has always been a cause of trouble in GnuPG because we used
only a very few functions and the complex include machinery of gnulib
is quite complex and the cause for many build problems for example on
OS X.  This is not gnulib's fault but due to our limited use of gnulib
and that we only rarely update the gnulib code to avoid regressions.

In part two we will address the functions

 mkdtemp
 setenv
 unsetenv
 strpbrk

which may bot be implemented on all platforms.  They are not required
on a libc based system.

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

g10/exec.c

@@ -48,7 +48,6 @@
 #include "i18n.h"
 #include "iobuf.h"
 #include "util.h"
-#include "mkdtemp.h"  /* From gnulib. */
 #include "membuf.h"
 #include "exec.h"