Update gpgme and gpg-error automake checks.
Pull updated autoconf files from the GPGME 1.13.0 release and use
those new macros.
Add a call to AM_PATH_GPG_ERROR() and include $(GPG_ERROR_LIBS) in the
libraries.
Thanks to Eike Rathke for finding the build problem, and for his
patch fixing the issue. I opted for just grabbing the newest autoconf
files from gpgme instead, but his fixed worked great too.