Fix address calculation for _DYNAMIC. We want to address of _DYNAMIC itself,

Fix address calculation for _DYNAMIC.  We want to address of _DYNAMIC itself,
not the address of its GOT entry.  The current code mixed the high bits of
the GOT entry address with the low bits of the true address.  This only
worked by accident for small binaries where _DYNAMIC and its GOT entry
happen to reside on the same page.

ok guenther@, mortimer@