Simplify a memcpy() in defragmentPage(). It now might copy more content than

Simplify a memcpy() in defragmentPage().  It now might copy more content than
is strictly necessary, but runs faster and uses less code space.  Possible
reasons for the improved performance:
(1) the copy is now always 8-byte aligned,
(2) fewer intermediate results are required which means less register
pressure which helps the compiler to optimize the subroutine.

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