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

abuf.h

@@ -1,8 +1,8 @@
 /*
  * abuf.h - append/prepend buffer utilities
  */
-#ifndef ABUF_H
-#define ABUF_H
+#ifndef KE_ABUF_H
+#define KE_ABUF_H
 
 #include <stddef.h>