* configure.ac: Remove unused test for GPG.
(ENABLE_KEYSERVER_SUPPORT): New ac_define and am_conditional.
(GPA_NAME): New.
* src/Makefile.am (keyserver_support_sources): New.  Move keyserver
related source files to here.
* src/confdialog.c (gpa_load_configured_keyserver)
(gpa_store_configured_keyserver): Take care of ENABLE_KEYSERVER_SUPPORT.
* src/gpaexportserverop.h, src/gpaimportserverop.h: Ditto.
* src/server-access.h: Ditto.
* src/gpgmetools.h (gpa_gpgme_warning_ext, gpa_gpgme_warning): New
macros.
* src/gpgmetools.c (gpa_gpgme_warning_ext): Rename to
(_gpa_gpgme_warning): this.  Add args FILE and LINE.
(gpa_gpgme_warning): Remove.
(gpa_start_simple_gpg_command): Improve error message.
* src/keymanager.c (key_manager_retrieve) [!ENABLE_KEYSERVER_SUPPORT]:
Disable.
(key_manager_send): Ditto.
(key_manager_action_new) [!ENABLE_KEYSERVER_SUPPORT]: Disable
keyserver stuff.