feat(*): support google closure compiler
feat(*): support google closure compiler

Because of duplicate definitions of getTranslateNamespace in the same scope, google
closure compiler returns the following error when minifying the angular-translate.js library
with the SIMPLE compilation_level:
  - Duplicate let / const / class / function declaration in the same scope is not allowed.
Change one of the getTranslateNamespace to be _getTranslateNamespace to avoid error.

angular-translate/angular-translate,angular-translate/angular-translate