Add espeak-ng (https://github.com/espeak-ng/espeak-ng)

Should close rfp#1066 (closed), if this was done correctly.

Reasons for the files in scanignore are given in com.reecedunn.espeak.yml: Every binary file in phsource was made by another open source program, espeakedit, found at http://espeak.sourceforge.net/download.html

(The other file listed under scanignore is a text file with three extraneous characters.)

EDIT: I forgot to mention that this recipe adds a dummy Gradle clean task so fdroid build will work properly. I suppose future versions will either have a real clean task or a different recipe, if this takes off. (I intended to add only the last stable release.) Not true anymore. The recipe uses very explicit instructions for the build now, most of them based on their own auto-generated Makefile.