Validate PackageInfo.g when loading packages

This helps package authors notice earlier if a package update
they made failed.

Author: fingolfin

lib/package.gi

@@ -1592,6 +1592,10 @@ InstallGlobalFunction( LoadPackage, function( arg )
           fi;
         fi;
 
+        if not ValidatePackageInfo(info) then
+           Print("#E Validation of package ", pkgname, " from ", info.InstallationPath, " failed\n");
+        fi;
+
         # Notify the documentation (for the available version).
         LoadPackageDocumentation( info );