patch 8.1.0514: CTRL-W ^ does not work when alternate buffer has no name

Problem:    CTRL-W ^ does not work when alternate buffer has no name.
Solution:   Use another method to split and edit the alternate buffer. (Jason
            Franklin)

Author: brammool

runtime/doc/windows.txt

@@ -222,9 +222,11 @@ CTRL-W CTRL_N						*CTRL-W_CTRL-N*
 		|:find|.  Doesn't split if {file} is not found.
 
 CTRL-W CTRL-^					*CTRL-W_CTRL-^* *CTRL-W_^*
-CTRL-W ^	Does ":split #", split window in two and edit alternate file.
-		When a count is given, it becomes ":split #N", split window
-		and edit buffer N.
+CTRL-W ^	Split the current window in two and edit the alternate file.
+		When a count N is given, split the current window and edit
+		buffer N.  Similar to ":sp #" and ":sp #N", but it allows the
+		other buffer to be unnamed.  This command matches the behavior
+		of |CTRL-^|, except that it splits a window first.
 
 						*CTRL-W_:*
 CTRL-W :	Does the same as typing |:| - enter a command line.  Useful in a

src/normal.c

@@ -5496,7 +5496,8 @@ nv_ctrlo(cmdarg_T *cap)
 }
 
 /*
- * CTRL-^ command, short for ":e #"
+ * CTRL-^ command, short for ":e #".  Works even when the alternate buffer is
+ * not named.
  */
     static void
 nv_hat(cmdarg_T *cap)