Specify CPUs on the PPC bswap-load-store test

Otherwise, the CHECK-NOT's might trigger depending on the host's CPU.
I believe debug mode for vector<T> (T != bool) is complete.  If anyone sees anything more they would like to see on it, please let me know.  Debug mode is activated by compiling with -D_LIBCPP_DEBUG2=1.  Eventually _LIBCPP_DEBUG2 will be renamed to just _LIBCPP_DEBUG.