Fix draw buffers support.

Bug 19353282

Change-Id: I6d1022c42a3347b8deb01af15078769d794050cb
Reviewed-on: https://swiftshader-review.googlesource.com/5146
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
3 files changed