CLEANUP: assorted typo fixes in the code and comments

This is 25th iteration of typo fixes
diff --git a/include/import/ebtree.h b/include/import/ebtree.h
index 36fcef5..9e5c488 100644
--- a/include/import/ebtree.h
+++ b/include/import/ebtree.h
@@ -32,7 +32,7 @@
 
   Eg, to store 8, 10, 12, 13, 14 :
 
-             ultree          this theorical tree
+             ultree          this theoretical tree
 
                8                   8
               / \                 / \