Fix some type links

Author: coke

doc/Language/control.rakudoc

@@ -292,7 +292,7 @@ over the more conventional C<my $username = …; if $username {…}>.
 Compare L<C<with>|/language/control#with>, which tests
 for definedness rather than truth, and topicalizes by default.
 (The second C<if> in the above example could be replaced by C<with> if the routine
-C<get-user-id> returned C<Nil> rather than 0 for nonexistent usernames.)
+C<get-user-id> returned L<C<Nil>|/type/Nil> rather than 0 for nonexistent usernames.)
 
 =head2 X<C<else/elsif>|Control flow,else elsif>
 

doc/Language/glossary.rakudoc

@@ -68,7 +68,7 @@ as shown in the following examples:
 
 Similarly to the angle brackets L<C«<…>»|/language/quoting#Word_quoting:_<_>> in the first line,
 other circumfix operators with their usual semantics can be used for stating the value,
-e.g. C<:foo[…]> for an array and C<:foo{…}> for a hash or even a L<Block|/type/Block>.
+e.g. C<:foo[…]> for an array and C<:foo{…}> for a hash or even a L<C<Block>|/type/Block>.
 With parentheses like in the second and third line, nearly all constructs can be used inside,
 notably L<quoting constructs|/language/quoting> and L<regexes|/language/regexes>.
 

doc/Language/signatures.rakudoc

@@ -489,8 +489,8 @@ so that even an instantiated L<C<Failure>|/type/Failure> acts as an undefined va
 
 =head2 Constraining signatures of L<C<Callable>|/type/Callable>s
 
-The signature of a L<Callable|/type/Callable> parameter can be constrained by
-specifying a L<Signature|/type/Signature> literal right after the parameter
+The signature of a L<C<Callable>|/type/Callable> parameter can be constrained by
+specifying a L<C<Signature>|/type/Signature> literal right after the parameter
 (no whitespace allowed):
 
     =begin code :skip-test<compile time error>
@@ -724,7 +724,7 @@ the signature to one of the following:
     (::T Numeric \a, T(Cool) \b )
 
 See also section L<method type_captures|/type/Parameter#method_type_captures>
-in the type reference for C<Parameter>.
+in the type reference for L<C<Parameter>|/type/Parameter>.
 
 
 X<|Language,positional argument>