contrib: bump opus to 1.2

Opus 1.2 brings many improvements, including
speech quality improvements, performance improvements,
and support for Ambisonics mapping, that could be used
for VR.

See https://people.xiph.org/~jm/opus/opus-1.2/

Using latest Opus has no major implication but
brings "free" quality and performance improvements and
is good for marketing purposes.

Change-Id: Ib7fa3ed17e423fffa8ac79f8fe8e3af46057991c

contrib/src/opus/SHA512SUMS

-57f14b9e8037eaa02a4d86535d3bbcceca249310fbc9ef1a452cc19dd442d4cf338d5db241d20605c236e22549df2c8266b7486c5f1666b80c532afd52cb3585  opus-1.1.4.tar.gz
+1bc8489012923c14fc38577c7b9c78368b627b088be55f6c7a40a825864da5006ec36c65686adbeba7e402fdc6ea793d6f1a6dfd281a2aadd79064ff07091ebc  opus-1.2.tar.gz

contrib/src/opus/fetch_and_patch.bat

 set BUILD=%SRC%..\build
 
-set OPUS_VERSION=b0dd440bbefa628e23ed50e418316c0afb4fe37d
+set OPUS_VERSION=4e59fb88fac0a4bfa616a7b1c2ec752baa610ef6
 set OPUS_URL=https://github.com/ShiftMediaProject/opus/archive/%OPUS_VERSION%.tar.gz
 
 mkdir %BUILD%

contrib/src/opus/rules.mak

 # opus
 
-OPUS_VERSION := 1.1.4
+OPUS_VERSION := 1.2
 
-OPUS_URL := http://downloads.xiph.org/releases/opus/opus-$(OPUS_VERSION).tar.gz
+OPUS_URL := https://archive.mozilla.org/pub/opus/opus-$(OPUS_VERSION).tar.gz
 
 PKGS += opus
 ifeq ($(call need_pkg,"opus >= 0.9.14"),)