Fix for Issue 6144.

This fixes Issue 6144 where `_output_cv_symbol_align` seg faults on `memcpy` call.

I have no idea what happens here but sometimes it works for > 15 KiB distance (up to 15964 once) and once it failed on ~14 KiB distance (14368 bytes). So let the safe distance be 8 KiB.

Issue URL: http://d.puremagic.com/issues/show_bug.cgi?id=6144