Get --old timezones into a usable and testable state

Hey,

Timezones like 'Etc/GMT+5' end up creating modules like 'DateTime/TimeZone/Etc/GMT+5.pm'. The problem here is that they are not valid Perl module names, so they can't be use'd. These changes fixes this, creates correct offsets, and allows "parse_olson --old" to pass all tests again.