Refactor out some individual functions in render_con() to make the code more readable.

include/render.h

@@ -10,6 +10,23 @@
  */
 #pragma once
 
+/* This is used to keep a state to pass around when rendering a con in render_con(). */
+typedef struct render_params {
+    /* A copy of the coordinates of the container which is being rendered. */
+    int x;
+    int y;
+
+    /* The computed height for decorations. */
+    int deco_height;
+    /* Container rect, subtract container border. This is the actually usable space
+     * inside this container for clients. */
+    Rect rect;
+    /* The number of children of the container which is being rendered. */
+    int children;
+    /* A precalculated list of sizes of each child. */
+    int *sizes;
+} render_params;
+
 /**
  * "Renders" the given container (and its children), meaning that all rects are
  * updated correctly. Note that this function does not call any xcb_*