Adds flunk and is-approx-calculate

The first had been left out accidentally, the second was
missing. Closes #2330.

doc/Type/Test.pod6

@@ -270,6 +270,17 @@ is-approx $value, $expected, :rel-tol<.5>, :abs-tol<10>;
 When both absolute and relative tolerances are specified, each will be
 tested independently, and the C<is-approx> test will succeed only if both pass.
 
+=head2 is-approx-calculate
+
+Defined as:
+
+    sub is-approx-calculate ($got,$expected,$abs-tol where { !.defined or $_ >= 0 },$rel-tol where { !.defined or $_ >= 0 },$desc)
+
+This is the actual routine called by
+L<C<is-approx> when absolute and relative tolerance are specified|/type/Test#Both_absolute_and_relative_tolerance_specified>.
+They are
+tested independently, and the test succeeds only if both pass.
+
 =head2 is-deeply
 
 Defined as:
@@ -752,6 +763,12 @@ Since these subroutines do not provide indication of what value was received
 and what was expected, they should be used sparingly, such as when evaluating
 a complex test condition.
 
+=head2 flunk
+
+    multi sub flunk($reason = '')
+
+The opposite of C<pass>, makes a test fail with an optional message.
+
 =head2 diag
 
     sub diag($message)