use the correct path separator on windows.

remove duplicates from the --plugin-load list.
$ENV{TERM} can be undefined (on Windows)

mysql-test/lib/mtr_cases.pm

@@ -621,6 +621,7 @@ sub process_opts {
   $tinfo->{$opt_name} = [];
 
   my @plugins;
+  my %seen;
 
   foreach my $opt (@opts)
   {
@@ -640,7 +641,8 @@ sub process_opts {
     $value= mtr_match_prefix($opt, "--plugin-load=");
     if (defined $value)
     {
-      push @plugins, $value;
+      push @plugins, $value unless $seen{$value};
+      $seen{$value}=1;
       next;
     }
 
@@ -685,7 +687,8 @@ sub process_opts {
   }
 
   if (@plugins) {
-    push @{$tinfo->{$opt_name}}, "--plugin-load=" . join(':', @plugins);
+    my $sep = (IS_WIN32PERL) ? ';' : ':';
+    push @{$tinfo->{$opt_name}}, "--plugin-load=" .  join($sep, @plugins);
   }
 }
 

mysql-test/mysql-test-run.pl

@@ -5840,7 +5840,7 @@ sub time_format($) {
 my $num_tests;
 
 sub xterm_stat {
-  if (-t STDOUT and $ENV{TERM} =~ /xterm/) {
+  if (-t STDOUT and defined $ENV{TERM} and $ENV{TERM} =~ /xterm/) {
     my ($left) = @_;
 
     # 2.5 -> best by test