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, and allows "parse_olson --old" to pass all tests again.

I'll have a look (possibly Monday) at actually getting valid values into them as I've just noticed that 'DateTime/TimeZone/Etc/GMT+5.pm' doesn't have it's correct offset values. At least the tests work again.