edify: do not set -std=gnu++11

Summary:
The build system applies LOCAL_CPPFLAGS on
parser.y and lexer.l, but c++ specific flags
can't be applied to them.

Test Plan: verified

Reviewers: randall.rushing, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D622

Change-Id: I54644054ff9cd8d8bebbea7a12f4a626b6261adb