Make appendToName do the right thing

I.e. append a suffix *before* the version, rather than after.  So we
get "sqlite-interactive-3.8.0.2" instead of
"sqlite-3.8.0.2-interactive".  The latter is broken since nix-env just
sees it the suffix as part of the version, so "nix-env -u" will
happily upgrade "sqlite-3.8.0.2-interactive" to "sqlite-3.9".