The export prologue goes into the _cgo_export.h file, where it may be
be #include'd by a .swig file. As SWIG defines its own type "intgo",
the definition of "intgo" in the export prologue could conflict.
Since we don't need to define "intgo" in the _cgo_export.h file, don't.

Defining "intgo" in _cgo_export.h was new for this release, so this
should not break any existing code.

No test case as I can't quite bring myself to write a test that
combines SWIG and cgo.

Change-Id: I8073e8300a1860cecd5994b9ad07dd35a4298c89
Reviewed-on: https://go-review.googlesource.com/83936
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>