sub MAIN and sub USAGE are collected to generate /routine/

Author: tisonkun

doc/Language/functions.pod6

@@ -879,7 +879,7 @@ print-bar Foo.new;
 Coercion types are supposed to work wherever types work, but Rakudo currently
 (2017.05) only implements them in signatures, for both parameters and return types.
 
-=head1 C<sub MAIN>
+=head1 sub MAIN
 X<|MAIN>X«|command line arguments»
 
 The sub with the special name C<MAIN> is executed after all relevant phasers,
@@ -932,7 +932,7 @@ positional parameter. For example, the above program can be called with:
 perl6 example.p6 1 --c=2 3 --d=4
 =end code
 
-=head1 C<sub USAGE>
+=head1 sub USAGE
 X<|USAGE>X<|$*USAGE>
 
 If no multi candidate of C<MAIN> is found for the given command line