[PATCH modular] Implement a classification for scripts using subdirectories

[Trevor Woerner]

The following is based on some of my assumptions, feel free to correct
as need be :-)

If the source tree wasn't so large I assume anyone building the code
would be expected to download the entire source and run a top-level
"./configure" and "make" once (like most any other project). I assume
when the modularization was taking place it was decided to make each
module shoudl be separate and stand-alone so a developer could work on
some subset and not have to download the entire source tree.

I assume the reason things like build.sh exist is because there is no
top-level ./configure script. A top-level configure script would be
able to sort out the dependencies and build everything in the correct
order, but it would expect all the code to be available since it would
need to generate files (e.g. Makefile) everywhere, even in submodules
which won't get built. So if there were a top-level ./configure script
it wouldn't be able to run unless all the code were available.
build.sh is more flexible in this way.

As a thought experiment, if we did use something like cmake would it
be able to solve the problem of not having to download and have
available all the code in order to build? Switching each of the
existing modules to cmake from the autotools wouldn't solve the
problem of not having a top-level cmake or ./configure script, would
it? We'd still need something to tie it nicely together and just build
and download a subset of the available code, no?