vulkan: implement vsync setting

src/modules/graphics/vulkan/Vulkan.cpp

@@ -7,6 +7,7 @@ namespace love {
 namespace graphics {
 namespace vulkan {
 static uint32_t numShaderSwitches;
+static int vsync = 1;
 
 void Vulkan::shaderSwitch() {
 	numShaderSwitches++;
@@ -20,6 +21,14 @@ void Vulkan::resetShaderSwitches() {
 	numShaderSwitches = 0;
 }
 
+void Vulkan::setVsync(int value) {
+	vsync = value;
+}
+
+int Vulkan::getVsync() {
+	return vsync;
+}
+
 VkFormat Vulkan::getVulkanVertexFormat(DataFormat format) {
 	switch (format) {
 	case DATAFORMAT_FLOAT: