ANGLE: Dynamically load D3D compiler from a list or the environment

If the default compiler cannot be found, load it from a list of DLL names.
On Desktop Windows, the default compiler can be specified by an
environment variable, QT_D3DCOMPILER_DLL. This can also be set at
compile time by a define of the same name. Otherwise, the default
compiler DLL is that which is set by the Direct3D SDK.

On WinRT, the default compiler is d3dcompiler_qt, which is a
non-versioned compiler proxy provided by Qt.

Change-Id: I0d7a8a8a36cc571836f8fa59ea14513b9b19c19b
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@digia.com>
ANGLE D3D11: Fix build on desktop Windows

This fixes a missing declaration caused by 11a2226c

Change-Id: I4b8092c6b9592e886353af9193686238105a1512
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@digia.com>