Make Blitter part of Renderer.

This fixes two issues. We had a global 'blitter' instance which doesn't
get destroyed until the library us unloaded. This is reported as a
memory leak (albeit benign). Potentially worse is that the singleton was
shared between all threads, and the Routine cache isn't thread safe.

Bug chromium:732691

Change-Id: I7b90d7d2bc67b4a9f78cdf4f54a76fa2f798b7cc
Reviewed-on: https://swiftshader-review.googlesource.com/10128
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
diff --git a/src/OpenGL/libGLESv2/main.cpp b/src/OpenGL/libGLESv2/main.cpp
index 348f361..3e6021c 100644
--- a/src/OpenGL/libGLESv2/main.cpp
+++ b/src/OpenGL/libGLESv2/main.cpp
@@ -93,14 +93,14 @@
 		return static_cast<es2::Context*>(context);
 	}
 
-	return 0;
+	return nullptr;
 }
 
 Device *getDevice()
 {
 	Context *context = getContext();
 
-	return context ? context->getDevice() : 0;
+	return context ? context->getDevice() : nullptr;
 }
 
 // Records an error code