Optimized function WebRtcSpl_ScaleAndAddVectorsWithRound() for ARM-NEON platforms, and refactor it for generic C.

We removed it out of ilbc_specific_functions.c, since it's used not only in iLBC.

Passed the unit test.
Review URL: https://webrtc-codereview.appspot.com/426009

git-svn-id: http://webrtc.googlecode.com/svn/trunk@1904 4adac7df-926f-26a2-2b94-8c16560cd09d
5 files changed