[svn-r6344] Add real error handling in MPIR_Localcopy to aid debugging in the field.
This adds two new macros, MPIU_MEM_RANGES_OVERLAP and MPIU_ERR_CHKMEMCPYANDJUMP, which can be used for error checking memcpy invocations in "mpi_errno" situations. Also refactor MPIU_MEM_CHECK_MEMCPY to use the new _RANGES_OVERLAP macro. This commit also uses CHKMEMCPYANDJUMP in MPIR_Localcopy so that we can figure out the code paths where we are missing alias checking when we get bug reports from users. Prior to this commit we would typically get assertion failures instead without a backtrace. No reviewer.