Adding a dummy column which is always set by the P() macro allows a single macro to be used for parameters or no parameters without violating C's prohibition on the {} initializer.
-Wmissing-field-initializers remains disabled because it still gives wildly different results between versions of gcc.
This documentation shows how to build a development environment on Ubuntu 19.04 and should work for other Debian-based distros.
Note that this document is not included in automated testing due to some unresolved issues with Docker in Docker on Travis CI. We'll address this in the future when we add contributing documentation to the website.
