Export missing init functions.
* src/gpg-error.h.in (gpgrt_init): New macro. (gpgrt_check_version): New prototype. * src/init.c (_gpg_err_init): Rename from gpg_err_init. (_gpg_err_deinit): Rename from gpg_err_deinit. * src/visibility.c (gpg_err_init): New. (gpg_err_deinit): New. (gpgrt_check_version): New. * src/gpg-error.vers (gpg_err_init, gpg_err_deinit): Add missing symbols. (gpgrt_check_version): New. * src/gpg-error.def.in (gpg_err_init, gpg_err_deinit): Add missing symbols. (gpgrt_check_version): New. * src/gpg-error.c (main): Use gpgrt_init macro.