mbrola: add mb-de8 voice

Makefile.am

 	espeak-ng-data/mbrola_ph/de2_phtrans \
 	espeak-ng-data/mbrola_ph/de4_phtrans \
 	espeak-ng-data/mbrola_ph/de6_phtrans \
+	espeak-ng-data/mbrola_ph/de8_phtrans \
 	espeak-ng-data/mbrola_ph/ee1_phtrans \
 	espeak-ng-data/mbrola_ph/en1_phtrans \
 	espeak-ng-data/mbrola_ph/es_phtrans \
 	mkdir -p espeak-ng-data/mbrola_ph
 	ESPEAK_DATA_PATH=$(PWD) src/espeak-ng --compile-mbrola=phsource/mbrola/de6
 
+espeak-ng-data/mbrola_ph/de8_phtrans: phsource/mbrola/de8 src/espeak-ng
+	mkdir -p espeak-ng-data/mbrola_ph
+	ESPEAK_DATA_PATH=$(PWD) src/espeak-ng --compile-mbrola=phsource/mbrola/de8
+
 espeak-ng-data/mbrola_ph/ee1_phtrans: phsource/mbrola/ee1 src/espeak-ng
 	mkdir -p espeak-ng-data/mbrola_ph
 	ESPEAK_DATA_PATH=$(PWD) src/espeak-ng --compile-mbrola=phsource/mbrola/ee1

docs/mbrola.md

 | `de5`        | German               | female | `mb-de5` | `mbrola-de5`   |
 | `de6`        | German               | male   | `mb-de6` | `mbrola-de6`   |
 | `de7`        | German               | female | `mb-de7` | `mbrola-de7`   |
-| `de8`        | German-Bavarian      | male   |          |                |
+| `de8`        | German-Bavarian      | male   | `mb-de8` |                |
 | `ee1`        | Estonian             | male   | `mb-ee1` | `mbrola-ee1`   |
 | `en1`        | British English      | female | `mb-en1` | `mbrola-en1`   |
 | `es1`        | Spanish              | male   | `mb-es1` | `mbrola-es1`   |

espeak-ng-data/voices/mb/mb-de8

+name german-mbrola-8
+language de 8
+gender male
+mbrola de8 de8_phtrans
+

phsource/mbrola/de8

+volume 12
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