Layers: They now compile on Windows.

Added missing vk funcs to basic and screenshot
Changed several funcs in mem_tracker to return void
Loader cmake file was generating .def file on linux, removed it
Fixed missing entry points in layers generated via python
diff --git a/layers/mem_tracker.cpp b/layers/mem_tracker.cpp
index e6f23f9..3dc7fb8 100644
--- a/layers/mem_tracker.cpp
+++ b/layers/mem_tracker.cpp
@@ -254,7 +254,7 @@
 //  Verify that (actual & desired) flags != 0 or,
 //   if strict is true, verify that (actual & desired) flags == desired
 //  In case of error, report it via dbg callbacks
-static bool32_t validate_usage_flags(void* disp_obj, VkFlags actual, VkFlags desired,
+static void validate_usage_flags(void* disp_obj, VkFlags actual, VkFlags desired,
                                      bool32_t strict, VkObject obj, VkObjectType obj_type,
                                      char const* ty_str, char const* func_name, char const* usage_str)
 {
@@ -272,7 +272,7 @@
 // Helper function to validate usage flags for images
 // Pulls image info and then sends actual vs. desired usage off to helper above where
 //  an error will be flagged if usage is not correct
-static bool32_t validate_image_usage_flags(void* disp_obj, VkImage image, VkFlags desired, bool32_t strict,
+static void validate_image_usage_flags(void* disp_obj, VkImage image, VkFlags desired, bool32_t strict,
                                            char const* func_name, char const* usage_string)
 {
     MT_OBJ_INFO* pInfo = get_object_info(image);
@@ -284,7 +284,7 @@
 // Helper function to validate usage flags for buffers
 // Pulls buffer info and then sends actual vs. desired usage off to helper above where
 //  an error will be flagged if usage is not correct
-static bool32_t validate_buffer_usage_flags(void* disp_obj, VkBuffer buffer, VkFlags desired, bool32_t strict,
+static void validate_buffer_usage_flags(void* disp_obj, VkBuffer buffer, VkFlags desired, bool32_t strict,
                                             char const* func_name, char const* usage_string)
 {
     MT_OBJ_INFO* pInfo = get_object_info(buffer);