Fix macos build
A bad copy-paste in later feature tests removed GNUTLS_CFLAGS and GNUTLS_LIBS from CFLAGS and LIBS too early, so the latest feature tests always fail. It manifests by having a public-key algorithm supported by gnutls but not present in the guile enumeration of public-key algorithms.
Also, CI is missing the texinfo homebrew formula.
Edited by Vivien Kraus