* spu/Makefile.in: Add new files.
* spu/jsre.h: Add JSRE_PREAD, JSRE_PWRITE, JSRE_READV, and
JSRE_WRITEV opcodes.
* spu/pread.c: New file to add pread via assist call.
* spu/pwrite.c: New file to add pwrite via assist call.
* spu/readv.c: New file to add readv via assist call.
* spu/writev.c: New file to add writev via assist call.
