Replaced per-sample validation define with global define in base class

Toggling validation via command line arguments is the preferred way anyway
Define was also added as a CMake option

examples/stencilbuffer/stencilbuffer.cpp

@@ -9,8 +9,6 @@
 #include "vulkanexamplebase.h"
 #include "VulkanglTFModel.h"
 
-#define ENABLE_VALIDATION false
-
 class VulkanExample : public VulkanExampleBase
 {
 public:
@@ -35,7 +33,7 @@ public:
 	VkDescriptorSet descriptorSet;
 	VkDescriptorSetLayout descriptorSetLayout;
 
-	VulkanExample() : VulkanExampleBase(ENABLE_VALIDATION)
+	VulkanExample() : VulkanExampleBase()
 	{
 		title = "Stencil buffer outlines";
 		timerSpeed *= 0.25f;