internal: update proto library version (#3025)

Also, two fixes:

- Fix long-standing `.travis.yml` bug where `VET_SKIP_PROTO` was not `export`ed (so not seen by `vet.sh`).
- Update `vet.sh` to work with new `goimports -l` that does not print a `:` after filenames.

Author: dfawley

.travis.yml

@@ -23,7 +23,7 @@ before_install:
   - if [[ "${GO111MODULE}" = "on" ]]; then mkdir "${HOME}/go"; export GOPATH="${HOME}/go"; fi
   - if [[ -n "${RUN386}" ]]; then export GOARCH=386; fi
   - if [[ "${TRAVIS_EVENT_TYPE}" = "cron" && -z "${RUN386}" ]]; then RACE=1; fi
-  - if [[ "${TRAVIS_EVENT_TYPE}" != "cron" ]]; then VET_SKIP_PROTO=1; fi
+  - if [[ "${TRAVIS_EVENT_TYPE}" != "cron" ]]; then export VET_SKIP_PROTO=1; fi
 
 install:
   - try3() { eval "$*" || eval "$*" || eval "$*"; }