Add info on difference between function pointer imports and function …

…type imports to the FAQ section (fixes #49)

doc/faq.qbk

@@ -95,6 +95,14 @@ But there's no guarantee that `filesystem::temp_directory_path()` will actually
 
 [pre
 ]
+
+* [*Question:] Can I use function pointer type (like `void(*)()`) instead of function type (like `void()`) to import function?
+  * [*Answer:] No you can't because the meaning of importing a function pointer is different:
+    * `lib.get<void()>("func")` imports a function `void func()`
+    * `lib.get<void(*)()>("func_var")` imports a variable that stores a pointer to the function `auto func_var = &func`
+
+[pre
+]
 
 * [*Question:]  I have found a bug, how do I notify?
   * [*Answer:]  Create an [@https://github.com/apolukhin/Boost.DLL/issues issue at GitHub] with a detailed description.