@foreach

Calls func with data for each buffer in this.

func can modify the passed buffer pointer or its contents. The return value of func defines if this function returns or if the remaining buffers in the list should be skipped.

Parameters:

this	a BufferList
func	a BufferListFunc to call
user_data	user data passed to func

Returns:

true when func returned true for each buffer in this or when this is empty.