7017454: Residual warnings in sun/nio/** and java/io native code (win64)

[Alan Bateman]

Whac-A-Mole time again with compiler warnings. This time its the VS2010 
compiler on Windows 64-bit, not sure how I missed these the last time. 
The webrev with the changes is here:
  http://cr.openjdk.java.net/~alanb/7017454/webrev/

Thanks,
Alan.