(compilation-buffer-p): Move defsubst before all callers.
(compilation-forget-errors): Reset compilation-parsing-end to 1 here.
(compile-reinitialize-errors): Don't reset compilation-parsing-end after
calling compilation-forget-errors.
Comment out gratuitous switch-to-buffer call; what was the rationale for it?
Don't check compilation-parsing-end (removed local AT-START); instead
always append to compilation-old-error-list, it will be nil if at start.
If compilation-error-list is non-nil before calling the parser, restore its
previous value afterwards; it still indicates the current error position.
Subtract the length of the existing compilation-error-list from
FIND-AT-LEAST when calling the parser.
(compilation-parse-errors): Don't check LIMIT-SEARCH at end of loop.
Inside check it inside each case of the cond; in error case we must discard
the last new error before stopping (just as for FIND-AT-LEAST).
Use floating-point in buffer percentage calculation, to avoid integer
overflow.