Add the dynamic target as a dependency in processPL

It needs the dependency to properly order the builds in a parallel
build.

Fixes #23

Makefile.PL

@@ -63,6 +63,7 @@ ReadKey.c: cchars.h
 sub MY::processPL {
  my $self = shift;
  $_ = $self->MM::processPL();
+ s/ReadKey.pm :: ReadKey_pm.PL/ReadKey.pm :: ReadKey_pm.PL dynamic/;
  s/\$\(PERLRUN\)/\$(FULLPERLRUNINST)/;
  $_
 }