Patch for cross-compiling DLLs on Ubuntu 14.04
Patch for cross-compiling DLLs on Ubuntu 14.04

I want to automatically cross-compile the Windows DLLs on Travis CI
(Ubuntu 14.04) to include them in the Github releases of java-libstorj.

The cross-compile fails on Ubuntu 14.04 unless the define declarations
in this PR are added to gnutls.mk.
Storj/libstorj-c,aleitner/libstorj-c,braydonf/libstorj,braydonf/libstorj-c,braydonf/libstorj-c,Storj/libstorj-c,aleitner/libstorj-c,braydonf/libstorj