Working on a convention for upcasting and downcasting in pseudo OO in C.

git-svn-id: svn://graphite/diminuto/trunk@572 5dfbf39a-1452-0410-8a97-9e58fedde8e3
26.0.1

git-svn-id: svn://graphite/diminuto/trunk@573 5dfbf39a-1452-0410-8a97-9e58fedde8e3