PATCH: Use __vdso_xxxx instead of xxxx for x86-64

[Roland McGrath]

> Are you sure this is the case for all kernels, even the earliest?  I
> think I added that code as-is because the __vdso_* names got
> introduced later.

Linux commit 2aae950b introduced the first proper vDSO on x86-64.
It has both foo and __vdso_foo names.  (In fact, the foo names
are weak aliases, and __vdso_foo is the primary name.)


Thanks,
Roland