patch 7.4.1087
Problem:    CTRL-A and CTRL-X do not work properly with blockwise visual
            selection if there is a mix of Tab and spaces.
Solution:   Add OP_NR_ADD and OP_NR_SUB. (Hirohito Higashi)
diff --git a/src/vim.h b/src/vim.h
index fd0b0b0..81d0929 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1457,6 +1457,10 @@
 #define OP_FOLDDELREC	25	/* "zD" delete folds recursively */
 #define OP_FORMAT2	26	/* "gw" format operator, keeps cursor pos */
 #define OP_FUNCTION	27	/* "g@" call 'operatorfunc' */
+#define OP_NR_ADD	28	/* "<C-A>" Add to the number or alphabetic
+				   character (OP_ADD conflicts with Perl) */
+#define OP_NR_SUB	29	/* "<C-X>" Subtract from the number or
+				   alphabetic character */
 
 /*
  * Motion types, used for operators and for yank/delete registers.