Move the declaration of DrawCall after Renderer.

Move the declaration of DrawCall after Renderer.

This allows compilers targeting the MS ABI to select the
correct inheritance model for the member function pointer field
DrawCall::setupPrimitives using the complete type of Renderer. It
will allow us to enable the new Clang flag -fcomplete-member-pointers
globally.

Bug: chromium:847724
Change-Id: Ied5859ec2f5d38b3ccf51608527506caec53f470
Reviewed-on: https://swiftshader-review.googlesource.com/19068
Tested-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>