NOIRLAB: Add SSL support to zfiond

[olebole]

This is adopted from the latest NOIRLAB commits, namely:

• b5c95b3 updated service URL for NOAO USNO cats
• ebe96c1 updates to handle chunked Transfer-Encoding responses
• 047474f removed unused args to nd_onsig(), type decl to fix linux warnings
• 3ae42f8 added TLS/SSL support for ZFIOND driver when OpenSSL transport available
• 5f84d1c updates to handle TLS/SSL transport
• fd47d7d modified to use url_get() to allow HTTPS services
• fee24f5 updates to use url_get(), updates to working catalog/image services
• 252cd09 added utility script for creating new services, see comments
• 5afae51 fix for openssl flags on macintel
• 0ef0543 added -DUSE_SSL flags for linux platforms
• 1f7c7bd added ifdef for SSL code
• f58de19 don't use SSL for linux 32-bit
• 26cdcaf fix for image cursor read

This adds a new non-standard dependency (openssl) to the build and to further use for development:

• on Linux systems, one needs to install libssl-dev (Debian).
• on macOS one needs to install f.e. homebrew, and to include the relevant include and library search paths. This must also be set when using xc.c; at least the link path.

The changes are used to update the catalogue retrieval for noao.astcat.

Todo

Make it work

It compiles, but cannot download https URLs ("ERROR: Cannot access template file or cannot make copy file"). This also does not work on NOIRLABs version 2.18.1/mac.

The urlget task uses fcadd, which however does not support https yet.

So we will wait with this PR to be functional before merge.

More code review

How to handle openSSL dependency on supported platforms:

• On Linux, (build) depend on openssl
• On Homebrew, depend on openssl
• For the native Mac build, copy the static openssl libs into lib$ and link to them in xc.
• For build from source, document how to switch on (or off) openssl