fix: most of make dist

There are (at least) one problem left: local installation of guile .go
files fail since `guile-config info sitedir` returns the actual installation
path whatever the --prefix given to configure.
Not sure how to fix this without imposing too much inconvenience.
chg: use pkg-config whenever possible (ie. for guile and openssl)

pkg-config allow to narrow a search to a given local path while
AC_CHECK_LIB will look anywhere for the library.