build: Relax requirements.
* m4/gpg-error.m4: Update from libgpg-error 1.33. * src/libassuan.m4: Don't require AM_PATH_GPG_ERROR. Only when gpgrt-config is available and works well, use it. * configure.ac (AM_PATH_GPG_ERROR): No requirement any more.
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>