Re: [Libvir] PATCH 2/5: Use pkg-config for gnutls

The current GNU TLS tests in the configure script just use CHECK_HEADER and CHECK_LIB to try and locate gnutls. This is fine if its in /usr, but no so useful if it is installed elsewhere. There are also no Makefile.am vars set to let you specify an alternate install location. gnutls already comes with support for pkg-config, so this patch just switches our configure script and Makefiles over to use that. Building against a different GNU TLS install is now just a matter of setting PKG_CONFIG_PATH, or the GNUTLS_LIBS and GNUTLS_CFLAGS vars.