patch 9.0.0067: cannot show virtual text

Problem:    Cannot show virtual text.
Solution:   Initial changes for virtual text support, using text properties.
diff --git a/src/regexp.c b/src/regexp.c
index f35a5e8..1a5cfd0 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -1303,7 +1303,7 @@
 	rex.line = reg_getline(rex.lnum);
 	rex.input = rex.line + col;
 
-	cols = win_linetabsize(wp, rex.line, col);
+	cols = win_linetabsize(wp, rex.reg_firstlnum + rex.lnum, rex.line, col);
 	if (cols < start || cols > end - (*p_sel == 'e'))
 	    return FALSE;
     }