Do the right thing when an ALLEGRO variable is defined,
and we're running under Windows, and we want a console.

Use it for allegro variants on Windows.
Also, use the console application build.exe on Windows (or buildi.exe as
appropriate) so that it's possible to capture Lisp standard output,
at the expense of not being able to run multithreaded code.

Document precisely why we (still) use that hack for LispWorks 7.0.0.

Disable previous hack, assuming that LW 7 now parses arguments correctly;
hopefully, we won't have to restore this hack after tests.

Also, require ASDF 3.1.2 and use package-inferred-system.
Move implementations database to a separate file
Import from asdf-tools (in asdf branch minimakefile) support for
Allegro variants and for composing strings of non-special characters.