Port dllexport markup changes from

 commit be660f46 (Try to fix MSVC8 link errors, 2007-08-28)
 commit 891bd2cb (Try again to get ncerr, ncopt working on Windows, 2007-08-28)
 commit 5c10a46e (Add dll exports for C++ version of netcdf, 2010-08-16)

forward to new netcdf import.

Change-Id: I3dd4894213adb60b38f87061172253802599b5dc