skip ignored files before callbacks

[technoweenie]

This updates listRecursive() to check the ignored or hidden status of a file path before calling the filter hooks. This can have massive CPU savings if the watcher ignores a massive sub directory in a recursively-watched directory.

It's also consistent with list():

watcher/watcher.go

Lines 260 to 272 in f5989f8

	if ignored || (w.ignoreHidden && isHidden) {
	continue
	}
	for _, f := range w.ffh {
	err := f(fInfo, path)
	if err == ErrSkip {
	continue outer
	}
	if err != nil {
	return nil, err
	}
	}