enable memcpy optimization for very large 16bpp COPY operations, add test cases
add align to 64 bits to 32BPP DECODE branch, this fixes a performance problem related to alignment that seems to have appeared as a result of the memcpy changes
name and align the DUP 32 bpp loop, alignment seems to improve performance for the special case loop though it is unclear exactly why
replace all compiler generated labels with named local labels, no logic changes
very slight performance advantage by adding 64 bit alignment to 16 bit DUP and DECODE blocks