Require at least libgpg-error 1.36

* configure.ac (NEED_GPG_ERROR_VERSION): Require 1.36.
* src/cJSON.c: Remove code for older version.
* src/engine.c (gpgme_get_engine_info): Ditto.
* src/gpgme-json.c: Ditto.
* src/op-support.c: Ditto.
* src/util.h: Ditto.

Libgpg-error 1.36 has been released more than 18 months ago so it is
time to avoid hacks and require this verion. This will for example
help Kleopatra to support PIV cards and improves the gpgme-json.

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