Remove code for Mac 10.5 and earlier from WTF and WebKit2
https://bugs.webkit.org/show_bug.cgi?id=113844

Reviewed by Benjamin Poulain.

Removed the code for 10.5 and removed if-def for 10.6.

Source/WebKit2: 

* Shared/mac/PasteboardTypes.mm:
(WebKit::PasteboardTypes::forEditing):

Source/WTF: 

* wtf/FastMalloc.cpp:
(WTF::TCMalloc_ThreadCache::CreateCacheIfNecessary):
* wtf/Platform.h:
* wtf/ThreadingPthreads.cpp:
(WTF::initializeCurrentThreadInternal):
* wtf/unicode/icu/CollatorICU.cpp:
(WTF::Collator::userDefault):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147525 268f45cc-cd09-0410-ab3c-d52691b4dbfc