Add port devel/p5-Readonly-XS:

The Readonly module (q.v.) is an effective way to create non-modifiable
variables. However, it's relatively slow.

The reason it's slow is that is implements the read-only-ness of variables
via tied objects. This mechanism is inherently slow. Perl simply has to do
a lot of work under the hood to make tied variables work.

This module corrects the speed problem, at least with respect to scalar
variables. When Readonly::XS is installed, Readonly uses it to access the
internals of scalar variables. Instead of creating a scalar variable object
and tying it, Readonly simply flips the SvREADONLY bit in the scalar's
FLAGS structure.

Readonly arrays and hashes are not sped up by this, since the SvREADONLY
flag only works for scalars. Arrays and hashes always use the tie interface.

Why implement this as a separate module? Because not everyone can use XS.
Not everyone has a C compiler. Also, installations with a statically-linked
perl may not want to recompile their perl binary just for this module.
Rather than render Readonly.pm useless for these people, the XS portion was
put into a separate module.

WWW: http://search.cpan.org/dist/Readonly-XS/

Justification: socialtext dependency