patch 8.2.2494: ":rviminfo!" clears most of oldfiles

Problem:    ":rviminfo!" clears most of oldfiles.
Solution:   Add VIF_ONLY_CURBUF to read_viminfo(). (closes #1781)
diff --git a/src/vim.h b/src/vim.h
index de2482e..73cb269 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2458,10 +2458,11 @@
 #define DOSO_GVIMRC	2	// loading gvimrc file
 
 // flags for read_viminfo() and children
-#define VIF_WANT_INFO		1	// load non-mark info
-#define VIF_WANT_MARKS		2	// load file marks
-#define VIF_FORCEIT		4	// overwrite info already read
-#define VIF_GET_OLDFILES	8	// load v:oldfiles
+#define VIF_WANT_INFO	    1	// load non-mark info
+#define VIF_WANT_MARKS	    2	// load file marks
+#define VIF_ONLY_CURBUF	    4	// bail out after loading marks for curbuf
+#define VIF_FORCEIT	    8	// overwrite info already read
+#define VIF_GET_OLDFILES    16	// load v:oldfiles
 
 // flags for buf_freeall()
 #define BFA_DEL		 1	// buffer is going to be deleted