Merge "Word the section about libc++ more strongly." into mnc-mr-docs am: 021c306
am: de5da71

* commit 'de5da71abc8538efaf19b8e209d63944498c9a79':
  Word the section about libc++ more strongly.

Change-Id: Id8a29bce564c7c617e1c1a872925ccc14ce5f173