Ported voices from NVSpeechPlayer to espeak variants.

espeak-ng-data/voices/!v/adam

+language variant
+name Adam
+klatt 6
+consonants 85 85
+
+formant 1 100 100 130

espeak-ng-data/voices/!v/benjamin

+language variant
+name Benjamin
+klatt 6
+consonants 70 70
+
+formant 1 101 100 130
+formant 2 102 100 100
+formant 3 100 100 100
+formant 4 100 100 100 470
+formant 5 100 100 100 350
+formant 6 100 100 100 100

espeak-ng-data/voices/!v/caleb

+language variant
+name Caleb
+klatt 6
+breath 100
+voicing 0

espeak-ng-data/voices/!v/david

+language variant
+name David
+klatt 6
+pitch 62 89
+
+formant 1 75 100 100
+formant 2 85 100 100
+formant 3 85 100 100