Quick and simple fix to make Variable-Magic pass again under blead.

Quick and simple fix to make Variable-Magic pass again under blead.

The test file t/18-opinfo.t in Variable-Magic makes some assumptions about
which ops are used to implement various perl constructs. A year ago, an
optimisation was added to the perl core in the form of the new
OP_PADSV_STORE op. Just recently in blead, v5.39.6-108-gc90e7ed39e, it
has been changed slightly so that the optimisation is only applied in void
context. The ops in 18-opinfo.t are called in scalar context, so the
optimisation is no longer applied, so the op is no longer what is
expected. The diff below just ensures that the three relevant expressions
are called in void context, ensuring that the optimisation still takes
place. This seemed an easier fix than adding further code along the lines
of 'if ($] > 5.0039006) ....', and will also not require further work if
the change in blead is reverted for whatever reason.