Fixes #3830: build failure on cygwin

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r29387 [[BR]]
Modify libevent to support cygwin - patch will be pushed upstream


r29388 [[BR]]
Avoid use of interface in struct because cygwin compilers apparently object (go figure)


r29389 [[BR]]
Ensure we add --no-undefined to libtool for cygwin
Fixes #3832: Fix CUDA-aware compile error on v1.7

Changed by patch