Tweak defaults for Chinese mode taken from the locale

- detect also the locale zh_SG as simplified Chinese
- if the Chinese variant is detected from the locale, set the
  Chinese mode to a mode which prefers a variant instead of
  showing that variant only. I.e., if zh_CN or zh_SG is in
  the locale, set the Chinese mode to 2 (“Show simplified Chinese first”)
  instead of 0 (“Show *only* simplified Chinese”).
  If one wants to show only one variant, one can easily change that
  later, but as a default it is better not to hide one variant, this
  seems to confuse some users who have not yet discovered that these
  options exist (see for example: https://code.google.com/p/ibus/issues/detail?id=1492
  and https://code.google.com/p/ibus/issues/detail?id=1670 )
- if no Chinese locale is set (and the Chinese mode is neither set in
  the table nor in the user settings either), use mode 4 (“Show all Chinese
  characters”) by default. In this case we don’t really know whether
  the table is intended for simplified or for traditional Chinese,
  it makes no sense to just guess simplified Chinese then.
Fix prompts for array30 table and don’t use prompts in pinyin mode

The array 30 table has prompts which are longer than one character.
Like this:

BEGIN_CHAR_PROMPTS_DEFINITION
q 1^
w 2^
e 3^
...
m 7v
, 8v
. 9v
/ 0v
END_CHAR_PROMPTS_DEFINITION

This did not work with my old code.

Also, do not use the prompts in pinyin mode. This commit

    commit c9f6a2bfe833da6f6a3d67546a89e0cefd886d83
    Author: Mike FABIAN <mfabian@redhat.com>
    Date:   Wed Jun 4 12:45:19 2014 +0200

	Don’t show the prompt characters defined in the table in pinyin mode in the auxiliary text

already avoided using the prompts in pinyin mode in the auxiliary text.
But prompt characters may also appear in the candidate list to show
which characters are needed to complete a candidate (“remaining_tabkeys”)
and also in the preëdit when no candidate can be found for the typed
characters.  Fix this for pinyin mode for these cases as well.
Update NEWS file for ibus-table 1.8.x
Make it possible to use select keys like F1, F2, F3 ...

Select keys like F1, F2, F3, ... are necessary for the ipa-x-sampa
table which has:

VALID_INPUT_CHARS == +!\%&'-./0123456789:<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_`abcdefghijklmnopqrstuvwxyz{|}~"

Therefore, using 1, 2, 3, ... as the select keys for ipa-x-sampa
is bad because it makes it impossible to input the following
entries of the ipa-x-sampa table:

    1	ɨ	0	### U+0268 LATIN SMALL LETTER I WITH STROKE
    2	ø	0	### U+00F8 LATIN SMALL LETTER O WITH STROKE
    3	ɜ	0	### U+025C LATIN SMALL LETTER REVERSED OPEN E
    3\	ɞ	0	### U+025E LATIN SMALL LETTER CLOSED REVERSED OPEN E
    4	ɾ	0	### U+027E LATIN SMALL LETTER R WITH FISHHOOK
    5	ɫ	0	### U+026B LATIN SMALL LETTER L WITH MIDDLE TILDE
    6	ɐ	0	### U+0250 LATIN SMALL LETTER TURNED A
    7	ɤ	0	### U+0264 LATIN SMALL LETTER RAMS HORN
    8	ɵ	0	### U+0275 LATIN SMALL LETTER BARRED O
    9	œ	0	### U+0153 LATIN SMALL LIGATURE OE

    _0	̥	0	### U+0325 COMBINING RING BELOW
    _1	₁	0	### U+2081 SUBSCRIPT ONE
    _2	₂	0	### U+2082 SUBSCRIPT TWO
    _3	₃	0	### U+2083 SUBSCRIPT THREE
    _4	₄	0	### U+2084 SUBSCRIPT FOUR
    _5	₅	0	### U+2085 SUBSCRIPT FIVE
    _6	₆	0	### U+2086 SUBSCRIPT SIX

Also, use the key codes of the select keys instead of the names of the
select keys in the key even processing. One could of course keep
using the names and still make using select keys like F1, F2, F3, ...
possible. But other similar key lists like self._commit_keys,
self._page_up_keys, and self._page_down_keys use key codes, it seems
nicer make all these similar key lists use the same data types.
For cangjie* and quick* tables: Use big5 order if the freq from the table is the same

In the cangjie5.txt table, all the frequency weights are 1000, for example:

    su	己	1000
    su	已	1000
    su		1000
    su	㔾	1000

Currently, the Unicode code point is used as a last ditch fallback if
all the other sort keys are the same (sort keys are: exact match, user
frequency, Chinese variant, system frequency, length of input
sequence, input sequence alphabetical, Unicode code point).

In case of the above characters matching “su”, the Unicode code
points and Big5 code points:

    㔾 U+353E Big5 -    Big5HKSCS 8BC8
    己 U+5DF1 Big5 A476 Big5HKSCS A476
    已 U+5DF2 Big5 A477 Big5HKSCS A477
     U+E81D Big5 -    Big5HKSCS -

Sorting via the Unicode code points gives:

    尸山 (1/9)
    1. 㔾
    2. 己
    3. 已
    4. 
    ...

And sorting first via the Big5 code points and then via the Unicode
code points for characters which do not have a Big5 code point gives:

    尸山 (1/9)
    1. 己
    2. 已
    3. 㔾
    4. 
    ...

This order seems to make more sense for Cangjie because:

• https://en.wikipedia.org/wiki/Big5:
  “The original Big5 character set is sorted first by usage frequency,
  second by stroke count, lastly by Kangxi radical.”
• some other popular operating system also uses Big5 order for Cangjie

Therefore, for the cangjie* and quick* tables, this commit introduces
another sort key sorting according to the Big5 code point just before
sorting the final sort key using the Unicode code point.

As the frequency data in the tables (which is currently always 1000
for cangjie5.txt, cangjie3.txt, and cangjie-big.txt) has higher priority,
one could still tweak the frequency data in the table if the order is
still not perfect for some characters. But it looks like Big5 order
is quite reasonable.
Merge pull request #43 from mike-fabian/tweak-defaults-for-chinese-mode-taken-from-locale

Tweak defaults for Chinese mode taken from the locale