(flymake-copy-buffer-to-temp-buffer): Simplify.

(flymake-copy-buffer-to-temp-buffer): Simplify.
(flymake-parse-output-and-residual): Remove `source-buffer' argument.
(flymake-process-filter): Switch to buffer before calling it instead.
(flymake-post-syntax-check, flymake-highlight-err-lines)
(flymake-delete-own-overlays, flymake-parse-err-lines)
(flymake-start-syntax-check, flymake-start-syntax-check-process)
(flymake-count-lines, flymake-parse-residual): Remove constant buffer argument.
(flymake-start-syntax-check-for-current-buffer): Remove.
Update callers to use flymake-start-syntax-check instead.
(flymake-display-err-menu-for-current-line): Remove unused var `mouse-pos'.
(flymake-restore-formatting): Comment out unused function.
(flymake-report-status, flymake-report-fatal-status): Remove buffer
argument, use current-buffer instead.  Update callers.