C API: Add SK_API, also documentation of an example.

include/c/sk_data.h

Index: include/c/sk_data.h
diff --git a/include/c/sk_data.h b/include/c/sk_data.h
index 90863ee8893c7b5da2b8f63ad98680091172e01f..95b7f5eb0ba7ee5782f7c98b265d0ce3ac82ea66 100644
--- a/include/c/sk_data.h
+++ b/include/c/sk_data.h
@@ -15,16 +15,16 @@
 
 SK_C_PLUS_PLUS_BEGIN_GUARD
 
-sk_data_t* sk_data_new_empty();
-sk_data_t* sk_data_new_with_copy(const void* src, size_t length);
-sk_data_t* sk_data_new_from_malloc(const void* memory, size_t length);
-sk_data_t* sk_data_new_subset(const sk_data_t* src, size_t offset, size_t length);
+SK_API sk_data_t* sk_data_new_empty();
+SK_API sk_data_t* sk_data_new_with_copy(const void* src, size_t length);
+SK_API sk_data_t* sk_data_new_from_malloc(const void* memory, size_t length);
+SK_API sk_data_t* sk_data_new_subset(const sk_data_t* src, size_t offset, size_t length);
 
-void sk_data_ref(const sk_data_t*);
-void sk_data_unref(const sk_data_t*);
+SK_API void sk_data_ref(const sk_data_t*);
+SK_API void sk_data_unref(const sk_data_t*);
 
-size_t sk_data_get_size(const sk_data_t*);
-const void* sk_data_get_data(const sk_data_t*);
+SK_API size_t sk_data_get_size(const sk_data_t*);
+SK_API const void* sk_data_get_data(const sk_data_t*);
 
 SK_C_PLUS_PLUS_END_GUARD