The previous delay code was incorrectly not utalising the whole buffer, causing glitches when
incressing the delay time, due to outputting incorrect data, This was apparent when using the
lfo in the Delay and Flanger plugins.
This has been rectified. The read index is now offset from the write index. and the complete buffer is used in a circular fashon.
Flanger - resolved issue where the lfo could create negative delay lengths
The original delay code, was setting it read index relative to the length
of the delay. This fixes that, now when the length is changed the read
index stays in the correct place in the buffer.
