Approved alternate source for 453.clvrleaf


Alternate source for compilers which have limited support for OpenACC "kernels" construct.

Src.alt removes use of the kernels construct and replace with an equivlent (where possible) use of the 
OpenACC parallel construct.  Due to the descriptive nature of parallel, not all schedules can be mapped
directly from kernels.  Best efforts were made but for some benchmarks, the parallel version may be
slower.
