patch 8.1.2169: terminal flags are never reset

Problem:    Terminal flags are never reset.
Solution:   Reset the flags when setting 'term'.

src/term.c

@@ -1957,6 +1957,8 @@ set_termname(char_u *term)
 #if defined(UNIX) || defined(VMS)
     term_is_xterm = vim_is_xterm(term);
 #endif
+    is_not_xterm = FALSE;
+    is_mac_terminal = FALSE;
 
 #ifdef FEAT_MOUSE
 # if defined(UNIX) || defined(VMS)

src/testdir/test_termcodes.vim

@@ -906,7 +906,18 @@ func Test_xx03_xterm_response()
   " Termresponse is only parsed when t_RV is not empty.
   set t_RV=x
 
+  " Do Terminal.app first to check that is_mac_terminal is reset.
+  set ttymouse=xterm
+  call test_option_not_set('ttymouse')
+  let seq = "\<Esc>[>1;95;0c"
+  call feedkeys(seq, 'Lx!')
+  call assert_equal(seq, v:termresponse)
+  call assert_equal('sgr', &ttymouse)
+
   " xterm < 95: "xterm" (actually unmodified)
+  set t_RV=
+  set term=xterm
+  set t_RV=x
   set ttymouse=xterm
   call test_option_not_set('ttymouse')
   let seq = "\<Esc>[>0;94;0c"

src/version.c

@@ -753,6 +753,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2169,
 /**/
     2168,
 /**/