gnatfind-opt, debug-pre-cmd and debug-post-cmd. Fix widget handling
for Emacs 21. ada-mode now only supports a single active project file,
instead of one per buffer. This is far less confusing.
(ada-prj-add-ada-menu): Remove the map and name parameters.
(ada-prj-display-page, ada-prj-field, ada-prj-initialize-values):
New function
(ada-prj-load-directory, ada-prj-subdirs-of): New functions
(ada-prj-load-from-file): New function
(ada-prj-save): Always save fields that depend on the current buffer
(ada-prj-show-value): New function
