libc: Update makefiles

Added includes and sources of libc to the makefiles.

Change-Id: I8e84db9634e0df7d51caa5c5858311672dd3a8d1
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
diff --git a/docs/design.rst b/docs/design.rst
index edb3c95..5a13d79 100644
--- a/docs/design.rst
+++ b/docs/design.rst
@@ -66,7 +66,7 @@
 
 -  **Library code.**
 
-   Firstly, there is ``include/stdlib/`` which provides standard C library
+   Firstly, there is ``include/libc/`` which provides standard C library
    functions like ``memcpy()``, ``printf()`` and so on.
    Additionally, various other APIs are provided under ``include/lib/``. The
    below list gives some examples but might not be exhaustive.