This waits for the user to release any modifier keys that are currently held before starting to type. This allows avoiding race conditions when xdotool is called from a keyboard shortcut, and starts to type characters with the modifier still held. Currently the usual way to do so is with --clearmodifiers, but this introduces its own race conditions (see e.g. issue jordansissel#43) if the physical key is released while the typing is in progress.

…ers, and add it to the manpage