Add console, klog, and writef modules.

They are not complete, but adding to checkpoint progress.

src/hulk/console.d

@@ -0,0 +1,72 @@
+/**
+ * HULK Console functionality.
+ */
+module hulk.console;
+
+import hulk.framebuffer;
+import hulk.kfont;
+
+struct Console
+{
+    Framebuffer * m_fb;
+    size_t m_width;
+    size_t m_height;
+    size_t m_x;
+    size_t m_y;
+
+    public void initialize(Framebuffer * fb)
+    {
+        m_fb = fb;
+        m_width = fb.width / kfont.advance;
+        m_height = fb.height / kfont.line_height;
+    }
+
+    public void clear()
+    {
+        m_fb.clear();
+        m_x = 0u;
+        m_y = 0u;
+    }
+
+    public void write(char ch)
+    {
+        if (ch == '\n')
+        {
+            m_x = 0u;
+            m_y++;
+        }
+        else
+        {
+            render_char(m_x, m_y, ch);
+            m_x++;
+            if (m_x == m_width)
+            {
+                m_x = 0u;
+                m_y++;
+            }
+        }
+        if (m_y == m_height)
+        {
+            m_y--;
+            m_fb.copy_rows_up(fb_y(m_height - 1u),
+                    (m_height - 1u) * kfont.line_height,
+                    kfont.line_height);
+        }
+    }
+
+    private void render_char(size_t x, size_t y, char ch)
+    {
+        const(CharInfo) * ci = &kfont.chars[ch];
+        m_fb.blit_alpha_bitmap(fb_x(x) + ci.left, fb_y(y) + ci.top - ci.height, ci.bitmap, ci.width, ci.height);
+    }
+
+    private size_t fb_x(size_t x)
+    {
+        return x * kfont.advance;
+    }
+
+    private size_t fb_y(size_t y)
+    {
+        return m_fb.height - ((y + 1u) * kfont.line_height);
+    }
+}