cpu: Support all platform-applicable assembly algorithms, even if used CFLAGS don't support them
cpu: Default to --algo auto
cpu: Add --algo fastauto (new default) to detect a usable algorithm without taking over a minute
README: Add missing documentation for CPU algorithms cryptopp_asm32, sse2_32, and altivec_4way
Merge branch '20130530_portablecpu' into bfgminer