* Update package: add info for emacs@26.1
In addition to the digest, it needs gnutls (perhaps there's a way to
turn it off, but it seems like a Good Thing to encourage, so...).
* Clean up tls variant handling
- Don't to specify the dependency for @26.1:, just need to fix what's
already there.
- Don't assume that configure will DTRT w.r.t. gnutls when it's
discovered in the environmnet, use explicit configure switches.
- Clean up some unnecessary dependencies when +tls. Why would you
need libxpm when building +tls? Will ask the original author about
this.
* Use append when adding configure switches
* Add dependency on pcre
When one builds +X, Spack's pcre is pulled into the build via
the X dependencies. When one builds without it, the build discovers
and links against the system library.
We might as well just depend on it and have a consistent outcome.
be8077367d