Add volkLoadInstanceOnly (#41)

* Add gitignore

* Add volkLoadInstanceOnly, fix warnings

Author: jkunstwald

.gitignore

@@ -0,0 +1,2 @@
+build/
+CMakeLists.txt.user

volk.c

@@ -104,6 +104,12 @@ void volkLoadInstance(VkInstance instance)
 	volkGenLoadDevice(instance, vkGetInstanceProcAddrStub);
 }
 
+void volkLoadInstanceOnly(VkInstance instance)
+{
+    loadedInstance = instance;
+    volkGenLoadInstance(instance, vkGetInstanceProcAddrStub);
+}
+
 VkInstance volkGetLoadedInstance()
 {
 	return loadedInstance;

volk.h

@@ -81,6 +81,12 @@ uint32_t volkGetInstanceVersion(void);
  */
 void volkLoadInstance(VkInstance instance);
 
+/**
+ * Load global function pointers using application-created VkInstance; call this function after creating the Vulkan instance.
+ * Skips loading device-based function pointers, requires usage of volkLoadDevice afterwards.
+ */
+void volkLoadInstanceOnly(VkInstance instance);
+
 /**
  * Load global function pointers using application-created VkDevice; call this function after creating the Vulkan device.
  *
@@ -92,13 +98,13 @@ void volkLoadDevice(VkDevice device);
  * Return last VkInstance for which global function pointers have been loaded via volkLoadInstance(),
  * or VK_NULL_HANDLE if volkLoadInstance() has not been called.
  */
-VkInstance volkGetLoadedInstance();
+VkInstance volkGetLoadedInstance(void);
 
 /**
  * Return last VkDevice for which global function pointers have been loaded via volkLoadDevice(),
  * or VK_NULL_HANDLE if volkLoadDevice() has not been called.
  */
-VkDevice volkGetLoadedDevice();
+VkDevice volkGetLoadedDevice(void);
 
 /**
  * Load function pointers using application-created VkDevice into a table.