Delete `eval-and-compile' around `require'.

Delete `eval-and-compile' around `require'.
Delete commented out code for old Emacs versions.
Autoloading of "ada-xref", "ada-prj" is useful even if compiler is not GNAT.
(ada-mode-version): Bump version number.
(ada-95-string-keywords, ada-2005-string-keywords, ada-2005-keywords,
ada-name-regexp): New constant.
(ada-language-version, ada-procedure-start-regexp, ada-mode,
ada-font-lock-keywords): Add support for Ada 2005 keywords.
(ada-package-start-regexp): Support private packages, include package
name (for ada-set-point-accordingly).
(ada-next-procedure, ada-previous-procedure, ada-which-function-are-we-in):
Match changes to ada-procedure-start-regexp.
(ada-make-body): Make non-interactive; not a user function.
(ada-make-subprogram-body): Improve doc string.