LibDraw: Introduce (formerly known as SharedGraphics.)

Instead of LibGUI and WindowServer building their own copies of the drawing
and graphics code, let's it in a separate LibDraw library.

This avoids building the code twice, and will encourage better separation
of concerns. :^)

Libraries/LibDraw/StylePainter.h

@@ -0,0 +1,31 @@
+#pragma once
+
+class Painter;
+class Rect;
+
+enum class ButtonStyle {
+    Normal,
+    CoolBar
+};
+enum class FrameShadow {
+    Plain,
+    Raised,
+    Sunken
+};
+enum class FrameShape {
+    NoFrame,
+    Box,
+    Container,
+    Panel,
+    VerticalLine,
+    HorizontalLine
+};
+
+class StylePainter {
+public:
+    static void paint_button(Painter&, const Rect&, ButtonStyle, bool pressed, bool hovered = false, bool checked = false, bool enabled = true);
+    static void paint_tab_button(Painter&, const Rect&, bool active, bool hovered, bool enabled);
+    static void paint_surface(Painter&, const Rect&, bool paint_vertical_lines = true, bool paint_top_line = true);
+    static void paint_frame(Painter&, const Rect&, FrameShape, FrameShadow, int thickness, bool skip_vertical_lines = false);
+    static void paint_window_frame(Painter&, const Rect&);
+};