speedo: Do not build gpgme anymore.

* build-aux/speedo.mk: Remove support gpgme.
* build-aux/speedo/w32/inst.nsi: Ditto.
* build-aux/speedo/w32/wixlib.wxs: Remove the gpgme components.

GPGME is either already availabale on Unix platforms or can be
installed on Widnows with gpg4win. GnuPG itself does not require
gpgme.