<string.h>, not <memory.h>, is the header file for memcpy().

<string.h>, not <memory.h>, is the header file for memcpy().

Don't include <memory.h> when using memcpy(), include <string.h>.

We don't need to check for memory.h, so don't do it in CMake (we don't
explicitly check for it in autoconf, but it's checked for by some macro
we do use).

Change-Id: I7aa93d4ea93bab9beff597939d3c24aecda3d52e
Reviewed-on: https://code.wireshark.org/review/7433
Reviewed-by: Guy Harris <guy@alum.mit.edu>