Use empty initializer lists for zeroing structs.

This works around an incorrect Clang warning:
https://llvm.org/bugs/show_bug.cgi?id=21689

Bug 15387371

Change-Id: I2460a4f6dd414f518789be1fcc8ce8b205c6a066
Reviewed-on: https://swiftshader-review.googlesource.com/4491
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>

src/Renderer/Renderer.cpp

diff --git a/src/Renderer/Renderer.cpp b/src/Renderer/Renderer.cpp
index 6ad2be3..49e856e 100644
--- a/src/Renderer/Renderer.cpp
+++ b/src/Renderer/Renderer.cpp
@@ -2522,7 +2522,7 @@
 		{
 			terminateThreads();
 
-			SwiftConfig::Configuration configuration = {0};
+			SwiftConfig::Configuration configuration = {};
 			swiftConfig->getConfiguration(configuration);
 
 			precacheVertex = !newConfiguration && configuration.precache;