Adjust relocation type secrel for w64 and fix base-file/dlltool functionality

[Nick Clifton]

Hi NightStrike, Hi Kai

> Was this applied yet?

No.  It has not been approved yet either.

Kai - what problem does this patch solve ?  How was it tested ?  Do you 
have a test case that can be added to the linker or binutils testsuites ?

One thing that concerns me is the changing of the R_AMD64_SECREL reloc. 
  Is this an ABI defined reloc ?

Cheers
   Nick