[1.29.07] Reduce clicks at very low pitches due to numerical overflow in wave generation.
Treat echo-delay = 0 as "no echo", even if ech-amplitude is set.
lang=ru, fix crash for "words" which has produce no phonemes (wg. ":").
git-svn-id: https://espeak.svn.sourceforge.net/svnroot/espeak/trunk@88 d46cf337-b52f-0410-862d-fd96e6ae7743