spe-samples builds!

Ok, it shouldn't be a important news in itself but creating an ebuild for it helped me getting a better idea on which are the pitfalls and issues of:

- autotools usage: probably would be better avoid that many configure and call the spu ones as they were cross building
- paths and prefixes: ppu- and plain spu- aren't that correct IMHO and seems config.sub shares my opinion...
- forcing -m{32|64} could be wrong when you try to embed spulets in ppc{32|63} elfs
- you shouldn't feed spu-elf-gcc with CFLAGS_ppc64 ...

Hopefully I'll try to get some of those issues clarified from upstream and/or fixed in an eclass or in the toolchain.