feat: openkal 0.5.1 and the four packages that are written against it - #224

Six packages, and the last two are what the first four exist to make possible.

  openkal          0.5.1   the specification: the declarations in C as well as
                           in modules, five error values, five operations and
                           two naming rules that a C library above it could not
                           be written without, and a conformance suite of 97
                           observations that an implementation runs against
                           itself
  openkal-linux    0.5.1   reimplemented on the kernel's own system-call
                           interface, so that a C library can sit above it
  openkal-macos    0.3.1   reimplemented on that kernel's own calls, and two
                           names no C library defines
  openkal-windows  0.1.1   new: an implementation on the Win32 interfaces and
                           the object manager beneath them, using no C runtime
                           symbol
  openkal-musl     0.3.0   musl 1.2.5 redirected onto openkal --- 1345 sources
                           compiled unmodified, four patched lines, nine
                           replaced sources
  sbase            0.1.0   new: the 97 suckless base utilities, sources
                           unmodified, running on Linux, macOS and Windows

sbase is the measurement rather than the demonstration. It has no Windows port
and does not build on macOS as it stands: three of its tools include a header of
the Linux C libraries and four use a field POSIX 2008 specifies that the other
system's C library does not have. Neither obstacle is in a kernel, and a C
library removes both by being present rather than by being adapted to. Fifty
comparisons against the system's own tools hold on all three.

Two version notes, both about a tag being the one thing that cannot be given a
second meaning. openkal 0.5.0 and its three implementations were tagged,
released and mirrored, and then found to carry files that describe a machine
rather than the package; the mirror allows neither replacing an asset nor
deleting a release, so the cleaned trees are 0.5.1, 0.3.1 and 0.1.1 and the
earlier tags are not carried here. openkal-musl was `openkal-libc' up to 0.2.0,
whose tags are still in that repository, so its first version under the new name
is 0.3.0; openkal-libc keeps its own descriptor for anything pinned to it.