Rename adler32_sse41 to adler32_ssse3

Rename adler32_sse41 to adler32_ssse3

As it turns out, the sum of absolute differences instruction _did_ exist
in SSSE3 all along. SSE41 introduced a stranger, less commonly used
variation of the sum of absolute difference instruction.  Knowing this,
the old SSSE3 method can be axed entirely and the SSE41 method can now
be used on CPUs only having SSSE3.

Removing this extra functable entry shrinks the code and allows for a
simpler planned refactor later for the adler checksum and copy elision.