patch 8.1.2012: more functions can be used as methods

Problem:    More functions can be used as methods.
Solution:   Make terminal functions usable as a method.  Fix term_getattr().
diff --git a/src/testdir/test_mksession.vim b/src/testdir/test_mksession.vim
index 62f1454..58e9cdd 100644
--- a/src/testdir/test_mksession.vim
+++ b/src/testdir/test_mksession.vim
@@ -408,7 +408,7 @@
 
 func Test_mksession_terminal_restore_other()
   terminal
-  call term_setrestore(bufnr('%'), 'other')
+  eval bufnr('%')->term_setrestore('other')
   mksession! Xtest_mks.out
   let lines = readfile('Xtest_mks.out')
   let term_cmd = ''