libvpx: 1.3.0 -> 1.4.0

* update SRC_URI
* remove re-definition of S
* drop backport patch 0001-configure.sh-quote-local-variables.patch
* update context of libvpx-configure-support-blank-prefix.patch

Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>