unsigned, since they can be positive or negative.
        
For better clarity, explicitly use ReturnPC instead of -1 as the "invalid"
state, since we'll never load and operate on the ReturnPC as a JS value.

* jit/JIT.cpp:
(JSC::JIT::JIT):
* jit/JIT.h:
* jit/JITInlineMethods.h:
(JSC::JIT::emitLoadTag):
(JSC::JIT::emitLoadPayload):
(JSC::JIT::emitLoad):
(JSC::JIT::emitLoad2):
(JSC::JIT::emitLoadDouble):
(JSC::JIT::emitLoadInt32ToDouble):
(JSC::JIT::emitStore):
(JSC::JIT::emitStoreInt32):
(JSC::JIT::emitStoreAndMapInt32):
(JSC::JIT::emitStoreCell):
(JSC::JIT::emitStoreBool):
(JSC::JIT::emitStoreDouble):
(JSC::JIT::map):
(JSC::JIT::unmap):
(JSC::JIT::isMapped):
(JSC::JIT::getMappedPayload):
(JSC::JIT::getMappedTag):
(JSC::JIT::emitJumpSlowCaseIfNotJSCell):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@100171 268f45cc-cd09-0410-ab3c-d52691b4dbfc