JSC: FunctionParameters are memory hungry.
<http://webkit.org/b/108033>
<rdar://problem/13094803>

Reviewed by Sam Weinig.

Instead of inheriting from Vector<Identifier>, make FunctionParameters a simple fixed-size array
with a custom-allocating create() function. Removes one step of indirection and cuts memory usage
roughly in half.

2.73 MB progression on Membuster3.

* bytecode/UnlinkedCodeBlock.cpp:
(JSC::UnlinkedFunctionExecutable::paramString):
* bytecompiler/BytecodeGenerator.cpp:
(JSC::BytecodeGenerator::BytecodeGenerator):
* parser/Nodes.cpp:
(JSC::FunctionParameters::create):
(JSC::FunctionParameters::FunctionParameters):
(JSC::FunctionParameters::~FunctionParameters):
* parser/Nodes.h:
(FunctionParameters):
(JSC::FunctionParameters::size):
(JSC::FunctionParameters::at):
(JSC::FunctionParameters::identifiers):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@140947 268f45cc-cd09-0410-ab3c-d52691b4dbfc