More fixes for Go bindings

Other fixes I needed to make to get the Go bindings mostly building. Mainly appear to be due to  changes to the Go toolchain over the past few years.


Also, I *think* the Makefile rule on line 5 (./go/Makefile) should be removed: 

    include ../rules.mk

Otherwise, one of the parent rules seems to override the `.so` targets, and the Go-specific rules don't get executed (like `go tool pack ...` etc.).