Control File: sub-package specification in standard control file

When writing a .info file, field names can be followed by a slash and the name of a sub-package as specified with the Sub-Package field.

However, if such a name appears in a standard control file, that's an error and the packager stops processing.

The following example shows what would work and not work in a standard control file (i.e. not a .info file):

VALIDPackage: wpkg
Description: Best packager around for MS-Windows

INVALIDPackage: wpkg
Description/core: Powerful packager for MS-Windows, manage thousands of packages seamlessly