Change the sdl_perl package name override.

The SDL perl module package in the official repository is the old
version of SDL perl bindings. These are in the SDL_Perl distribution.
The new version is simply called SDL. We don't want to confuse the
two.

lib/CPANPLUS/Dist/Arch.pm

@@ -71,7 +71,7 @@ Gnome2-Canvas  = gnomecanvas-perl
 Gtk2           = gtk2-perl
 mod_perl       = mod_perl
 Pango          = pango-perl
-SDL            = sdl_perl
+SDL_Perl       = sdl_perl
 Perl-Critic    = perl-critic
 Perl-Tidy      = perl-tidy
 App-Ack        = ack