Remove custom allocator support from PODArena
https://bugs.webkit.org/show_bug.cgi?id=115762

Reviewed by Andreas Kling.

Nobody uses PODArena with a custom allocator, so just get rid of it and always use fastMalloc/fastFree.

* platform/PODArena.h:
(WebCore::PODArena::PODArena):
(WebCore::PODArena::allocateBase):
(WebCore::PODArena::Chunk::Chunk):
(WebCore::PODArena::Chunk::~Chunk):
(Chunk):
* platform/PODFreeListArena.h:
(WebCore::PODFreeListArena::allocate):
(WebCore::PODFreeListArena::FreeListChunk::FreeListChunk):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149695 268f45cc-cd09-0410-ab3c-d52691b4dbfc