cdrom.eclass: Detect case-insensitively and handle special characters

cdrom.eclass: Detect case-insensitively and handle special characters

This eclass previously used "find -iname" but it only checked the file
case-insensitively and not the directories. There is "find -ipath" but
this does not intelligently skip non-matching paths, making it
slow. Globbing is used here instead.

The : character has always been used to delimit paths given to
cdrom_get_cds, which makes sense because : generally isn't allowed on
CDs, while whitespace is. Despite that, whitespace was not being
handled properly and neither were wildcard characters. Now all special
characters are automatically escaped.