GL,ShaderTools: add missing include.

Got broken by Macros.h removed from Corrade/Utility/Debug.h.

doc/snippets/MagnumShaderTools.cpp

@@ -29,6 +29,7 @@
 #include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/String.h>
 #include <Corrade/Containers/StringStl.h> /** @todo drop when file callbacks are <string>-free */
+#include <Corrade/Utility/Macros.h> /* CORRADE_LINE_STRING */
 #include <Corrade/Utility/Resource.h>
 
 #include "Magnum/FileCallback.h"

src/Magnum/GL/Context.cpp

@@ -30,6 +30,7 @@
 #include <Corrade/Containers/GrowableArray.h>
 #include <Corrade/Utility/Arguments.h>
 #include <Corrade/Utility/Debug.h>
+#include <Corrade/Utility/Macros.h> /* CORRADE_THREAD_LOCAL */
 
 #include "Magnum/GL/AbstractFramebuffer.h"
 #include "Magnum/GL/AbstractShaderProgram.h"