Added command line flag "--bitcode-as-text", and triggered
the acceptance of textual bitcode on this flag. To make sure
this isn't added to the sandboxed translator, the reading of
bitcode text is also dependent on the translator not being a
minimal build.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4222
R=jvoung@chromium.org, stichnot@chromium.org

Review URL: https://codereview.chromium.org/1215463014 .