Included patch for persistent undo. Lots of changes and added test.

src/option.h

@@ -815,6 +815,7 @@ static char *(p_ttym_values[]) = {"xterm", "xterm2", "dec", "netterm", "jsbterm"
 # define TTYM_JSBTERM		0x10
 # define TTYM_PTERM		0x20
 #endif
+EXTERN char_u	*p_udir;	/* 'undodir' */
 EXTERN long	p_ul;		/* 'undolevels' */
 EXTERN long	p_uc;		/* 'updatecount' */
 EXTERN long	p_ut;		/* 'updatetime' */
@@ -1004,6 +1005,7 @@ enum
     , BV_TS
     , BV_TW
     , BV_TX
+    , BV_UDF
     , BV_WM
     , BV_COUNT	    /* must be the last one */
 };