Experimental rate reducing for letters
Use maximal speed for speaking letters and tts_say.
voiceman-emacspeak: fixed handling of multiline commands

Multiline text in Tcl commands was concatenated without any intervening
whitespace. This fix makes it add space.
1.5.0.3

General:
- The patch by Dmitri Paduchikh  to reduce letters processing rate;
- The patch by Dmitri Paduchikh  to fix line breaks processing in emacspeak protocol;
- Configuration file parameter "letters at min rate in [Global]" section added;
- Environment variable $VOICEMAN_EMACSPEAK_TTS_SAY_AT_MIN_RATE for emacspeak client added;
- libao checking for ./configure script added.