Import icu4c 52.1.
Subtree-merge branch 'vendor/icu4c' into icu4c-integration
Update ICU Visual Studio projects to 2013.

Also switch to using v120_xp toolset.
Organize dependencies into folders in Poedit.sln.
Add missing Berkeley DB reference to Visual Studio project.
Ignore ICU build files on Windows.
Build ICU dependency on OS X.
Enable MultiProcessorCompilation for deps VS projects.
Enable recommended ICU settings for C++.

See http://source.icu-project.org/repos/icu/icu/trunk/readme.html#RecBuild
Disable unused ICU features.
ICU compilation fixes for custom build settings.

Patches submitted to upstream:
http://bugs.icu-project.org/trac/ticket/10498
http://bugs.icu-project.org/trac/ticket/10499
http://bugs.icu-project.org/trac/ticket/10500
Link with ICU, include its runtime in distribution files.
Add helpers for ICU<->wxString conversion.

Add helper functions for efficient (when possible, i.e.  on Windows)
conversion between wxString and icu::UnicodeString.
Merge branch 'icu4c-integration' into better-languages-handling
Improve Visual Studio incremental linking.

See http://blogs.msdn.com/b/vcblog/archive/2013/10/30/the-visual-c-linker-best-practices-developer-iteration.aspx
Show error if the Language header is missing.

The header is important for lot of stuff, it really should be set, so
try to convince the user as best as we can.
Use std::bind/function instead of boost now that C++11 is required.
Refactor: rename lang_info to language, put generated content into another file.
Nicer AttentionBar on Windows.

Add a subtle border to make it stand out a bit more. Use bold font.
Add Language class for better representation.

Instead of keeping the language code as a string and parsing it in
various places, use a symbolic representation that can have all the
smarts in one place.

Also allows integration with ICU, e.g. for (already used) display names.