AtkValue: refactoring AtkValue

In summary:
  * Stop to use GValue to get/set the value and use doubles instead
  * Include the support for a string description and subranges

https://bugzilla.gnome.org/show_bug.cgi?id=684576
AtkValue: add a testvalue example, with a small AtkValue
 implementation

https://bugzilla.gnome.org/show_bug.cgi?id=684576
atkvalue: add strings to translate value type names
Updated Norwegian bokmål translation
Updated POTFILES.in
Updated Polish translation
Updated Brazilian Portuguese translation
Updated Galician translations
Add translations notes to atkvalue.c
Updated Hungarian translation
Updated Korean translation
Updated Spanish translation
Updated Latvian translation
Updated Chinese (China) translation
Updated Lithuanian translation
Updated Traditional Chinese translation(Hong Kong and Taiwan)
Updated Czech translation
Updated Portuguese translation
atk/atk.symbols: Make up for the Missed Symbols

There were some added public APIs for AtkValue, which was not updated to
atk/atk.symbols, so make up for them.

https://bugzilla.gnome.org/show_bug.cgi?id=726216
autotools: Ensure Needed Sources Are Distributed

atk/atkprivate.h and tests/teststateset.c were missed from the source
distribution, so make up for them to fix the build.

https://bugzilla.gnome.org/show_bug.cgi?id=726216