Stack guards are too conservative
https://bugs.webkit.org/show_bug.cgi?id=115147

Reviewed by Mark Hahnenberg.

Source/JavaScriptCore:

Increase stack guard to closer to old size.

* interpreter/Interpreter.cpp:
(JSC::Interpreter::StackPolicy::StackPolicy):

Source/WTF:

Use getrlimit on darwin to get the stack size for the main thread.

* wtf/StackBounds.cpp:
(WTF::StackBounds::initialize):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149146 268f45cc-cd09-0410-ab3c-d52691b4dbfc