Added code do generate and request windows structures that describe the function and it's prolog. This unwind information is used by windows to unwind the stack when it has to generate a call stack (in case of an exception or in the debugger).
This can be used like:

  PRUNTIME_FUNCTION pruntimefunction;
  DWORD64           baseaddress;

  if ( jit_function_compile(func) && jit_get_function_boundaries(func, (void**)&pruntimefunction, (void**)&baseaddress))
  {
    RtlAddFunctionTable(pruntimefunction, 1, baseaddress);
  }

and when you free the function:
  RtlDeleteFunctionTable(pruntimefunction);

Note that at leas Visual Studio 2005 does not use this information to show the correct call stack in the debugger. WinDbg and Visual Studio 2010 do (did not try 2008).