new features:
- cmd/gop: refactor gop mod tidy
- gop: gop.NewImporter
- ast: gop/ast/mod
changes:
- cmd/gop: gop c2go => gop c
- cmd/gop: gop go/build/install/run/test: use fmt.Fprintf instead of panic
- cl: improve prompt of struct member not found
- mod: mod v0.9.7; c2go v0.7.2; libc v0.3.6
incompatible changes: