Libraries: Create top level directory for libraries.

Things were getting a little crowded in the project root, so this patch
moves the Lib*/ directories into Libraries/.

Libraries/LibGUI/GTextBox.cpp

@@ -0,0 +1,10 @@
+#include <LibGUI/GTextBox.h>
+
+GTextBox::GTextBox(GWidget* parent)
+    : GTextEditor(GTextEditor::SingleLine, parent)
+{
+}
+
+GTextBox::~GTextBox()
+{
+}