Fix for RT#47980

Adam Kennedy opened a ticket against Module::Build, which David Golden correctly
interpreted as being version.pm's fault (in the pure Perl release only).  I've
committed a change (and test) that will be part of version-0.77.  The matching
fix needs to be applied to Module::Build's inline code.

John

=== lib/Module/Build/Version.pm
==================================================================
--- lib/Module/Build/Version.pm	(revision 2640)
+++ lib/Module/Build/Version.pm	(local)
@@ -628,15 +628,17 @@
     my $class = ref($obj) || $obj;

     no strict 'refs';
-    eval "require $class" unless %{"$class\::"}; # already existing
-    return undef if $@ =~ /Can't locate/ and not defined $req;
+    unless (%{"$class\::"}) { # class not already loaded
+    	eval "require $class";
+    	return undef if $@ =~ /Can't locate/ and not defined $req;
+    }

     if ( not %{"$class\::"} and $] >= 5.008) { # file but no package
 	require Carp;
 	Carp::croak( "$class defines neither package nor VERSION"
 	    ."--version check failed");
     }
-
+
     my $version = eval "\$$class\::VERSION";
     if ( defined $version ) {
 	local $^W if $] <= 5.008;