feature/gbuild_ure needs testing

[David Tardon]

Hi all,

now that 3.6.0 is sucessfully out, I have started pushing gbuild
conversion forward again. The latest result of my effort is on branch
feature/gbuild_ure and you really do want to test that it works on your
platform :-) What is there:

1/ Module bridges has been converted to gbuild. This module is _crucial_
   for UNO. Have I already said that you want to test the branch? The
   absolute minimum to check that C++ bridge still works is to run

   make testtools.all

2/ Module cli_ure has been converted to gbuild. Actually I have created
   some machinery for building CLI stuff in gbuild, because it seemed to
   make more sense than copy-pasting (nearly) the same code several
   times. This only builds on windows. I do expect some problems, because
   I only smoketested the code (replacing all commands by touch $@).

3/ 21 modules have been added to tail_build. I hope that I have found
   and fixed all incomplete dependencies, but it is possible that some
   additional ones arise on different platforms/configurations.

If you find a problem, yell at me or fix it :-)

D.