voices: Change default number pronunciation rule to enabled.

docs: add details about number flags to the documentation.

It's clearly intended to be enabled by default:
- it's defined as default behaviour translate.h (NUM_DEFAULT)
- tr_languages.c sets many default values related to number processing
  that have no meaning unless langopts.numbers == 1.

It is also a more sensible default since most languages will want to
have number processing on. This makes adding new languages easier
because  adding an entry to tr_languages.c is unnecessary.

A negative side effect is that languages with partial number defines
might experience bugs when reading undefined numbers. This is a bug and
should be fixed.

This will have the side effect of enabling number processing for
languages that currently have it disabled. However, there shouldn't be
any.

Here's a way to check affected languages:
for voice in $(ESPEAK_DATA_PATH=`pwd` LD_LIBRARY_PATH=src:${LD_LIBRARY_PATH}
src/espeak-ng --voices | grep -v Languages | awk '{print $2}'); do
OUTPUT=$(ESPEAK_DATA_PATH=`pwd` LD_LIBRARY_PATH=src:${LD_LIBRARY_PATH}
src/espeak-ng -qx -v $voice "1 - 2 - 3 - 12 - 123") && echo "$voice:
$OUTPUT" ; done

These voices clearly benefit from enabling numbers (they already have
number rules in *_list):
ba, cmn (zh), hak, haw, ja, kok, nb, nci

Some languages are missing some definitions (like _12) in _list files.
It causes the program to skip some numbers.
Numbering needs to be turned off explicitly for:
jbo, mi, my, piqd, py, qu, quc, th, uz

Languages with no number rules at all:
chr, cv, he, nog, tk, ug

docs/numbers.md

 
 These controls how numbers are pronounced.
 
-If `numbers` is set to `0` (the default value), numbers will not be pronounced.
-Setting it to `1` will enable number pronunciation using the dictionary rules.
+If `numbers` is set to `0`, numbers will not be pronounced.
+Setting it to `1` (the default value) will enable number pronunciation using the dictionary rules.
+For more control over number pronunciation, see the flags in `translate.h`.
+
 
     tr->langopts.max_digits
 

src/libespeak-ng/tr_languages.c

  * Copyright (C) 2005 to 2015 by Jonathan Duddington
  * email: [email protected]
  * Copyright (C) 2015-2016, 2020 Reece H. Dunn
+ * Copyright (C) 2021 Juho Hiltunen
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
 	tr->langopts.min_roman = 2;
 	tr->langopts.thousands_sep = ',';
 	tr->langopts.decimal_sep = '.';
+	tr->langopts.numbers = NUM_DEFAULT;
 	tr->langopts.break_numbers = BREAK_THOUSANDS;
 	tr->langopts.max_digits = 14;
 
 
 	switch (name2)
 	{
+	case L('m', 'i'):
+	case L('m', 'y'):
+	case L4('p', 'i', 'q', 'd'): // piqd
+	case L('p', 'y'):
+	case L('q', 'u'):
+	case L3('q', 'u', 'c'):
+	case L('t', 'h'):
+	case L('u', 'z'):
+	{
+		tr->langopts.numbers = 0; // disable numbers until the definition are complete in _list file
+	}
+		break;
 	case L('a', 'f'):
 	{
 		static const short stress_lengths_af[8] = { 170, 140, 220, 220,  0, 0, 250, 270 };
 		tr->langopts.param[LOPT_CAPS_IN_WORD] = 1; // capitals indicate stressed syllables
 		SetLetterVowel(tr, 'y');
 		tr->langopts.max_lengthmod = 368;
+		tr->langopts.numbers = 0; // disable numbers until the definition are complete in _list file
 	}
 		break;
 	case L('k', 'a'): // Georgian