Major codebase cleanup and overhaul.

+ editor removes per-buffer fields.
+ switching from internal use of 'int' to 'size_t'.
+ deleting old code
+ double checking relevancy of comments. A lot has changed in
  5 years, even more so in the past week.
+ fixing a few vestigal memory errors from the overhaul.
+ fixing search behavior

undo.c

@@ -1,8 +1,10 @@
+#include <assert.h>
+#include <stdlib.h>
 #include "abuf.h"
 #include "undo.h"
 
 
-undo_node
+undo_node *
 undo_node_new(undo_kind kind)
 {
 	undo_node	*node = NULL;
@@ -13,10 +15,12 @@ undo_node_new(undo_kind kind)
 	node->kind = kind;
 	node->row = node->col = 0;
 
-	abuf_init(node->text);
+	ab_init(&node->text);
 	
 	node->next = NULL;
 	node->parent = NULL;
+
+	return node;
 }
 
 
@@ -26,11 +30,10 @@ undo_node_free(undo_node *node)
 	undo_node	*next = NULL;
 
 	if (node == NULL) {
-		return NULL;
+		return;
 	}
 
-	abuf_free(node-text);
-	next = node->next;
+	ab_free(&node->text);
 }
 
 
@@ -44,9 +47,10 @@ undo_node_free_all(undo_node *node)
 	}
 
 	while (node != NULL) {
+		next = node->next;
 		undo_node_free(node);
 		free(node);
-		node = node->next;
+		node = next;
 	}
 }
 
@@ -65,7 +69,7 @@ undo_tree_init(undo_tree *tree)
 void
 undo_tree_free(undo_tree *tree)
 {
-	assert(tree == NULL);
+	assert(tree != NULL);
 
 	undo_node_free(tree->pending);
 	undo_node_free_all(tree->root);
@@ -86,19 +90,25 @@ undo_begin(undo_tree *tree, undo_kind kind)
 		undo_commit(tree);
 	}
 
-	pending = undo_new_new(kind);
+	pending = undo_node_new(kind);
 	assert(pending != NULL);
 
 	tree->pending = pending;
 }
 
 
-void		 undo_prepend(abuf *buf);
-void		 undo_append(buf *buf);
-void		 undo_prependch(char c);
-void		 undo_appendch(char c);
-void		 undo_commit(void);
-void		 undo_apply(undo_node *node);
-void		 editor_undo(void);
-void		 editor_redo(void);
+void
+undo_prepend(undo_tree *tree, abuf *buf)
+{
+
+}
+
+
+void		 undo_append(undo_tree *tree, abuf *buf);
+void		 undo_prependch(undo_tree *tree, char c);
+void		 undo_appendch(undo_tree *tree, char c);
+void		 undo_commit(undo_tree *tree);
+void		 undo_apply(struct editor *editor);
+void		 editor_undo(undo_tree *tree);
+void		 editor_redo(undo_tree *tree);