Temporarily disable libopencv due to upstream compile error

There is a know upstream ffmpeg compile error when enabling
libopencv. It should compile opencv code in C++ mode but it
is compiling in C mode. Disabling libopencv support while a
fix is not provided either by upstream ffmpeg or by opencv
repository package.

References:
-----------
http://trac.ffmpeg.org/ticket/7059
https://github.com/opencv/opencv/issues/10963
https://bugs.archlinux.org/task/57811

.SRCINFO

@@ -1,7 +1,7 @@
 pkgbase = ffmpeg-full
 	pkgdesc = Record, convert and stream audio and video (all possible features including nvenc, qsv and libfdk-aac)
 	pkgver = 3.4.2
-	pkgrel = 4
+	pkgrel = 5
 	url = http://www.ffmpeg.org/
 	arch = i686
 	arch = x86_64
@@ -37,7 +37,6 @@ pkgbase = ffmpeg-full
 	depends = libmodplug
 	depends = lame
 	depends = opencore-amr
-	depends = opencv
 	depends = openjpeg2
 	depends = opus
 	depends = pulseaudio

PKGBUILD

@@ -4,7 +4,7 @@
 pkgname=ffmpeg-full
 _srcname=ffmpeg
 pkgver=3.4.2
-pkgrel=4
+pkgrel=5
 pkgdesc='Record, convert and stream audio and video (all possible features including nvenc, qsv and libfdk-aac)'
 arch=('i686' 'x86_64')
 url='http://www.ffmpeg.org/'
@@ -15,7 +15,7 @@ depends=(
         'bzip2' 'frei0r-plugins' 'libgcrypt' 'gmp' 'gnutls' 'ladspa' 'libass'
         'libbluray' 'libcaca' 'celt' 'libcdio-paranoia' 'libdc1394' 'libavc1394'
         'libfdk-aac' 'fontconfig' 'freetype2' 'fribidi' 'libgme' 'gsm' 'libiec61883'
-        'libmodplug' 'lame' 'opencore-amr' 'opencv' 'openjpeg2' 'opus' 'pulseaudio'
+        'libmodplug' 'lame' 'opencore-amr' 'openjpeg2' 'opus' 'pulseaudio'
         'librsvg' 'rubberband' 'rtmpdump' 'smbclient' 'snappy' 'libsoxr' 'speex'
         'libssh' 'tesseract' 'libtheora' 'twolame' 'v4l-utils' 'vid.stab' 'libvorbis'
         'libvpx' 'wavpack' 'libwebp' 'libx264.so' 'x265' 'libxcb' 'xvidcore' 'libxml2'
@@ -142,7 +142,7 @@ build() {
         --enable-libmp3lame \
         --enable-libopencore-amrnb \
         --enable-libopencore-amrwb \
-        --enable-libopencv \
+        --disable-libopencv \
         --enable-libopenh264 \
         --enable-libopenjpeg \
         --enable-libopenmpt \