code cleanup: remove dead code related to Tibetan

Language 'bo' has no data files. Tibetan might have been supported
before but clearly isn't any longer.

phsource/ph_tibetan

-
-phoneme a
-  vwl starttype #a endtype #a
-  length 180
-  FMT(vowel/a)
-endphoneme
-
-phoneme e
-  vwl starttype #e endtype #e
-  length 180
-  FMT(vowel/e_mid2)
-endphoneme
-
-phoneme i
-  vwl starttype #i endtype #i
-  length 180
-  FMT(vowel/i)
-endphoneme
-
-phoneme o
-  vwl starttype #o endtype #o
-  length 180
-  FMT(vowel/o)
-endphoneme
-
-phoneme u
-  vwl starttype #u endtype #u
-  length 180
-  FMT(vowel/u)
-endphoneme
-
-
-
-
-
-phoneme ts
-  vls alv afr sib
-  voicingswitch dz
-  lengthmod 2
-  Vowelin f1=0  f2=1700 -300 300  f3=-100 80
-  Vowelout f1=0 f2=1700 -300 250  f3=-100 80  rms=20
-  IF nextPh(isPause2) THEN
-    WAV(ustop/ts2)
-  ENDIF
-  WAV(ustop/ts2)
-endphoneme
-
-
-phoneme dz
-  vcd alv afr sib
-  voicingswitch ts
-  lengthmod 5
-  Vowelin f1=1  f2=1700 -300 300  f3=-100 80 len=50
-  Vowelout f1=2 f2=1700 -300 300  f3=-100 80
-
-  IF PreVoicing THEN
-    FMT(d/xd)
-  ENDIF
-
-  IF nextPh(isPause2) THEN
-    FMT(voc/z_) addWav(ustop/ts2, 60)
-  ENDIF
-  FMT(d/xdz) addWav(ustop/ts2, 140)
-endphoneme
-
-phoneme ts#
-  vls alv afr sib
-  voicingswitch dz
-  lengthmod 2
-  Vowelin f1=0  f2=1700 -300 300  f3=-100 80
-  Vowelout f1=0 f2=1700 -300 250  f3=-100 80  rms=20
-  IF nextPh(isPause2) THEN
-    WAV(ustop/ts_)
-  ENDIF
-  WAV(ustop/ts)
-endphoneme
-
-
-phoneme dz#
-  vcd alv afr sib
-  voicingswitch ts
-  lengthmod 5
-  Vowelin f1=1  f2=1700 -300 300  f3=-100 80 len=50
-  Vowelout f1=2 f2=1700 -300 300  f3=-100 80
-
-  IF PreVoicing THEN
-    FMT(d/xd)
-  ENDIF
-
-  IF nextPh(isPause2) THEN
-    FMT(voc/z_) addWav(ustop/ts_, 60)
-  ENDIF
-  FMT(d/xdz) addWav(ustop/ts, 140)
-endphoneme
-

phsource/phonemes

 phonemetable hi hi_base
 include ph_hindi
 
-phonemetable bo hi
-include ph_tibetan
-
 phonemetable gd base1 // hidden dependency, imports from hi
 include ph_s_gaelic
 

src/libespeak-ng/tr_languages.c

 			tr->langopts.numbers2 = NUM2_SWAP_THOUSANDS;
 		}
 
-	}
-		break;
-	case L('b', 'o'): // Tibet
-	{
-		tr->langopts.stress_rule = STRESSPOSN_1L;
-		tr->letter_bits_offset = OFFSET_TIBET;
-		SetLetterBitsRange(tr, LETTERGP_A, 0x71, 0x7d); // vowel signs
-		SetLetterBitsRange(tr, LETTERGP_B, 0x71, 0x81); // vowel signs and subjoined letters
-		SetLetterBitsRange(tr, LETTERGP_B, 0x90, 0xbc);
-		SetLetterBitsRange(tr, LETTERGP_C, 0x40, 0x6c); // consonant letters (not subjoined)
-		tr->langopts.param[LOPT_UNPRONOUNCABLE] = 1;    // disable check for unpronouncable words
-		tr->langopts.numbers = NUM_DEFAULT;
 	}
 		break;
 	case L3('c', 'h', 'r'): // Cherokee