Don't run change.t and md5.t below 5.10.

In 5.8.[2-9] there is an error on non-threaded perls with "can't locate
structure for statement", and I can't be bothered track it down and fix or
work around it.  Let's just bump the minimum recommended version to 5.10, and
keep 5.6.1 and 5.8 as "best effort".

tests/change.t

@@ -15,8 +15,13 @@ use File::Copy;
 use Devel::Cover::Inc;
 use Devel::Cover::Test;
 
-if ($] == 5.008007)
-{
+if ($] < 5.010) {
+    eval "use Test::More skip_all => 'Test requires perl 5.10.0 or greater'";
+    # can't locate structure for statement
+    exit;
+}
+
+if ($] == 5.008007) {
     eval "use Test::More skip_all => 'Crashes 5.8.7'";
     exit;
 }
@@ -27,22 +32,16 @@ my $t  = "change";
 my $ft = "$base/tests/$t";
 my $fg = "$base/tests/trivial";
 
-my $run_test = sub
-{
+my $run_test = sub {
     my $test = shift;
 
     copy($fg, $ft) or die "Cannot copy $fg to $ft: $!";
-
     $test->run_command($test->test_command);
 
-    # sleep 1;
-
     copy($fg, $ft) or die "Cannot copy $fg to $ft: $!";
-
     open T, ">>$ft" or die "Cannot open $ft: $!";
     print T <<'EOT';
-sub new_sub
-{
+sub new_sub {
     my $y = 1;
 }
 
@@ -54,11 +53,10 @@ EOT
     $test->run_command($test->test_command);
 };
 
-my $test = Devel::Cover::Test->new
-(
+my $test = Devel::Cover::Test->new(
     $t,
-    run_test => $run_test,
-    end      => sub { unlink $ft },
+    run_test  => $run_test,
+    end       => sub { unlink $ft },
     no_report => 0,
 );
 

tests/md5.t

@@ -15,40 +15,38 @@ use File::Copy;
 use Devel::Cover::Inc;
 use Devel::Cover::Test;
 
+if ($] < 5.010) {
+    eval "use Test::More skip_all => 'Test requires perl 5.10.0 or greater'";
+    # can't locate structure for statement
+    exit;
+}
+
+if ($] == 5.008007) {
+    eval "use Test::More skip_all => 'Crashes 5.8.7'";
+    exit;
+}
+
 my $base = $Devel::Cover::Inc::Base;
 
 my $t  = "md5";
 my $ft = "$base/tests/$t";
 my $fg = "$base/tests/trivial";
 
-if ($] == 5.008007)
-{
-    eval "use Test::More skip_all => 'Crashes 5.8.7'";
-    exit;
-}
-
-my $run_test = sub
-{
+my $run_test = sub {
     my $test = shift;
 
     copy($fg, $ft) or die "Cannot copy $fg to $ft: $!";
-
     open T, ">>$ft" or die "Cannot open $ft: $!";
     print T "# blah blah\n";
     close T or die "Cannot close $ft: $!";
-
     $test->run_command($test->test_command);
 
-    # sleep 1;
-
     copy($fg, $ft) or die "Cannot copy $fg to $ft: $!";
-
     $test->{test_parameters} .= " -merge 1";
     $test->run_command($test->test_command);
 };
 
-my $test = Devel::Cover::Test->new
-(
+my $test = Devel::Cover::Test->new(
     $t,
     run_test => $run_test,
     end      => sub { unlink $ft },