Reviewed by Benjamin Poulain.

Upstream iOS WebKit Source/WTF.

* Configurations/Base.xcconfig:
JavaScriptCore.framework is a public framework.

* wtf/Assertions.h:
Define an export macro for iOS projects just including <wtf/Assertions.h>.

* wtf/Platform.h:
* wtf/FeatureDefines.h:
iOS ENABLE and USE defines.

* wtf/MainThread.h:
* wtf/mac/MainThreadMac.mm:
(WTF::initializeApplicationUIThreadIdentifier):
(WTF::initializeWebThreadIdentifier):
(WTF::canAccessThreadLocalDataForThread):
* wtf/WeakPtr.h:
(WTF::WeakReference::get):
(WTF::WeakReference::clear):
Shared WebThread and MainThread access to thread local data.

* wtf/WTFThreadData.cpp:
(WTF::WTFThreadData::WTFThreadData):
Shared WebThread and MainThread identifier tables.

* wtf/ThreadSpecific.h:
(WTF::::replace):
Used later on so that WebThread can share the MainThread's thread global data.

* wtf/text/StringStatics.cpp:
(WTF::AtomicString::init):
When USE(WEB_THREAD) assert AtomicString::init is initialized on the realMainThread.

* wtf/unicode/CharacterNames.h:
* wtf/unicode/icu/UnicodeIcu.h:
(WTF::Unicode::hasLineBreakingPropertyComplexContextOrIdeographic):
Minor iOS constants and functions used later by WebCore.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154294 268f45cc-cd09-0410-ab3c-d52691b4dbfc