*** Linux Users ***
Sorry I suck, if you want to use AVX or XOP in Linux you will need to compile 
the code with a new-ish GCC I know it works on version 4.6.1 (in Cygwin). 
"revxsha1-32" and "revxsha1-64" were compiled with GCC 4.4.4 which doesn't 
support AVX.

*** Windows Users ***
Also "rev xsha1.exe" is 32 bit because I suck. You will need to compile the 
64 bit version your self. Make sure you set the correct compile flags for 
xsha1avx.cpp and xsha1xop.cpp. Also note that the 64 bit version is only a 
little bit faster than the 32 bit version (in Linux).

*** Everyone ***
I haven't tested AVX or XOP so it may not work correctly, but the chances of 
that are slim.
