Layout:

  specs/

Contains sources to C programs, which when compiled, emit Perl code
describing the size of various types and constructs, formatted as a
blob of code suitable for adding to the end of a .ph file.

"make" compiles specs/* to bin/*, and then executes bin/*
generating appends/*

"h2ph" is then invoked to generate "headers/*"

and entries in appends/* are combined with entries in headers/* to produce
appended/*

Subsequent deployment of such is left to the user.