List of changes:
-added a minor optimization to the Simulator that quickly skips nops in the delay slot
-slightly re-worked CEntryStub to save a few instructions
 CEntryStub now expects the following values:
  -s0: number of arguments including receiver
  -s1: size of arguments excluding receiver
  -s2: pointer to builtin function
 Two new MacroAssembler functions were added to make usage more convenient:
  -PrepareCEntryArgs(int num_args) to set up s0 and s1
  -PrepareCEntryFunction(const ExternalReference&) to set up s2
-removed branch delay slot nops from the most frequently used code areas
-reorganized some code to execute fewer instructions
-utilized the delay slot of most Ret instructions
 This does not cover all Rets, only the most obvious cases.
 Also added a special version of DropAndRet that utilizes the delay slot.
-added some comments to code areas where explanation of the register/delay slot usage may be needed
-added an optimization to Jump so it doesn't always pre-load the target register

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/9699071
Patch from Daniel Kalmar <kalmard@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11099 ce2b1a6d-e550-0410-aec6-3dcde31c8c00