Downstream packaging patchset

[leamas]

EDIT: Rewritten docs after a rebase update.

An admittedly large patch set from the downstream Debian packaging:

• Fix the missing so-version i. e., a defined ABI level (#194)
• Add some standard cmake configuration, PROJECT, PUBLIC_HEADER etc.
• Add an official configuration switch ENABLE_TEST_PROGRAM to build the test program
• Probe for doxygen, use it to build the docs if available.
• Make the CATKIN_ENABLE_TESTING an official option, makes it visible in cmake help etc.
• Don't include the ubiquitous v8stdint.h in package unless its' actually used.
• Add an option to build using the alternative package name cxx-serial to avoid name conflicts when using the generic serial, by default off.
• Fix the timing tests, now works on both MacOS and Linux.
• ci updates:
  • Add a travis build on Ubuntu Focal (as of today, all travis builds are broken). The existing, broken builds are left as-is after refactoring .travis.yml (#230). Update the xenial config to build a catkin package
  • Add a appveyor.yml configuration building the win32 library
  • Add a circleci configuration building Macos.

Closes: #194 Closes: #232 Closes: #230

These changes (besides the ci updates) will go into an upcoming Debian version. The current 1.2.1-3 contains a limited set.

Travis build logs Focal, Xenial CircleCI build logs: MacOS, Focal

The patches are reasonably separate, cherry-picking should be possible.

[leamas]

Rebased & enhanced. See initial comment (edited)

[wjwwood]

Not sure I can take this in the current form, but I'll try to incorporate each of these things in the next version where I will be redoing CI (with GitHub Actions) and removing the catkin support in favor of pure CMake.