DL_DEBUG_UNUSED buggy, especially with vdso

[David Miller]

From: David Miller <davem@davemloft.net>
Date: Wed, 04 Apr 2012 02:22:59 -0400 (EDT)

> From: David Miller <davem@davemloft.net>
> Date: Tue, 03 Apr 2012 23:59:32 -0400 (EDT)
> 
>> 2) Dealing with the PLT lazy eval issue.  We can't just pretend
>>    LD_BIND_NOW is set because in this test case testobj1.so also
>>    references a symbol 'foo' via the PLT which will be undefined
> 
> And this addresses the PLT lazy eval issue.
> 
> Any objections?

I'm extremely confident in these two fixes, and they get unused dep
analysis actually working again on all platforms.  Could someone
please review them?

Thanks.