Remove support for the GPG_AGENT_INFO envvar.

* agent/agent.h (opt): Remove field use_standard_socket.
* agent/command.c (cmd_killagent): Always allow killing.
* agent/gpg-agent.c (main): Turn --{no,}use-standard-socket and
--write-env-file into dummy options.  Always return true for
--use-standard-socket-p. Do not print the GPG_AGENT_INFO envvar
setting or set that envvar.
(create_socket_name): Simplify by removing non standard socket
support.
(check_for_running_agent): Ditto.
* common/asshelp.c (start_new_gpg_agent): Remove GPG_AGENT_INFO use.
* common/simple-pwquery.c (agent_open): Ditto.
* configure.ac (GPG_AGENT_INFO_NAME): Remove.
* g10/server.c (gpg_server): Do not print the AgentInfo comment.
* g13/server.c (g13_server): Ditto.
* sm/server.c (gpgsm_server): Ditto.
* tools/gpgconf.c (main): Simplify by removing non standard socket
support.
--

The indented fix to allow using a different socket than the one in the
gnupg home directory is to change Libassuan to check whether the
socket files exists as a regualr file with a special keyword to
redirect to another socket file name.

configure.ac

@@ -104,7 +104,6 @@ use_exec=yes
 use_trust_models=yes
 card_support=yes
 use_ccid_driver=yes
-use_standard_socket=yes
 dirmngr_auto_start=yes
 use_tls_library=no
 
@@ -707,30 +706,6 @@ fi
 AM_CONDITIONAL(USE_LDAPWRAPPER, test "$use_ldapwrapper" = yes)
 
 
-#
-# Allows enabling the use of a standard socket by default This is
-# gpg-agent's option --[no-]use-standard-socket.  For Windows we force
-# the use of this.
-#
-AC_MSG_CHECKING([whether to use a standard socket by default])
-AC_ARG_ENABLE(standard-socket,
-              AC_HELP_STRING([--disable-standard-socket],
-                             [don't use a standard socket by default]),
-              use_standard_socket=$enableval)
-tmp=""
-if test "$use_standard_socket" != yes; then
-  if test "$have_w32_system" = yes; then
-    use_standard_socket=yes
-    tmp=" (forced)"
-  fi
-fi
-AC_MSG_RESULT($use_standard_socket$tmp)
-if test "$use_standard_socket" = yes; then
-  AC_DEFINE(USE_STANDARD_SOCKET,1,
-            [Use the standard socket for the agent by default])
-fi
-
-
 # (These need to go after AC_PROG_CC so that $EXEEXT is defined)
 AC_DEFINE_UNQUOTED(EXEEXT,"$EXEEXT",[The executable file extension, if any])
 
@@ -1615,8 +1590,6 @@ AC_DEFINE_UNQUOTED(GPGCONF_DISP_NAME, "GPGConf",
 
 AC_DEFINE_UNQUOTED(GPGTAR_NAME, "gpgtar", [The name of the gpgtar tool])
 
-AC_DEFINE_UNQUOTED(GPG_AGENT_INFO_NAME, "GPG_AGENT_INFO",
-                   [The name of the agent info envvar])
 AC_DEFINE_UNQUOTED(GPG_AGENT_SOCK_NAME, "S.gpg-agent",
                    [The name of the agent socket])
 AC_DEFINE_UNQUOTED(GPG_AGENT_SSH_SOCK_NAME, "S.gpg-agent.ssh",
@@ -1802,7 +1775,6 @@ echo "
         Default scdaemon:  $show_gnupg_scdaemon_pgm
         Default dirmngr:   $show_gnupg_dirmngr_pgm
 
-        Use standard socket: $use_standard_socket
         Dirmngr auto start:  $dirmngr_auto_start
         Readline support:    $gnupg_cv_have_readline
         DNS SRV support:     $use_dns_srv