(font-lock): Don't require any more.

(font-lock): Don't require any more.
(compilation-error-properties, compilation-start, compilation-sentinel)
(compilation-filter, next-error): Use with-current-buffer.
(compilation-skip-to-next-location, compilation-skip-threshold)
(compilation-skip-visited): Move to silence the byte-compiler.
(compilation-setup): Simplify.
(compilation-next-error): Use line-(beginning|end)-position.
Make sure `pt' is non-nil before using compilation-loop.
(compile-goto-error): Add optional event arg.  Use it.
(compile-mouse-goto-error): Make it an alias of compile-goto-error.
(compilation-minor-mode-map, compilation-shell-minor-mode-map):
Update the binding for mouse-2.
(first-error): Set compilation-current-error to nil rather than bob.
(compilation-parsing-end, compilation-parse-errors-function)
(compilation-error-list, compilation-old-error-list):
"New" compatibility variables.
(compile-buffer-substring, compilation-compat-error-properties)
(compilation-compat-parse-errors, compilation-forget-errors):
New compatibility functions.
(compilation-mode-font-lock-keywords): Use them.