[Emacs-ada-mode] ADA_PROJECT_PATH

[Stephen Leake]

I set ADA_PROJECT_PATH uniquely for each Ada project; one uses GtkAda,
another Windex, another GWindows. In addition, I change it for debug
vs release; there is a 'windex.gpr' in both $WINDEX/build/debug and
$WINDEX/build/release, for example. ADA_PROJECT_PATH determines which
one is used.

Currently, I set ADA_PROJECT_PATH in my Makefiles. But for people who
don't do Makefiles, I think it makes sense to add a new option in
ada-mode project files:

    ada_project_path=<directory>

This would be a list, like src_dir. It would export the environment
variable ADA_PROJECT_PATH when the ada-mode project file is read;
ADA_PROJECT_PATH would then be used by gnatgpr and gnatmake when
ada-mode invokes them.

Then we have a standard way of specifying ADA_PROJECT_PATH, which can
be configured in CVS (or monotone, for Ludovic :).

We could also specify ADA_INCLUDE_PATH and ADA_OBJECT_PATH, when they
are needed.

-- 
-- Stephe