Fixed Etc/UTC timezone recognition, updated tests

[ellenaua]

This is a fix for issue #598

Why issue happened

• in 2017c unpacked data, "Etc/UTC" is going before "Etc/Universal" in array
• in 2018d unpacked data, "Etc/Universal" is going before "Etc/UTC" in array
  Because of this, in 2017c packed data links are:

"Etc/UCT|UCT",
"Etc/UTC|Etc/Universal",
"Etc/UTC|Etc/Zulu",
"Etc/UTC|UTC",
"Etc/UTC|Universal",
"Etc/UTC|Zulu",

but in 2018d it linked this way:

"Etc/Universal|Etc/UTC",
"Etc/Universal|Etc/Zulu",
"Etc/Universal|UTC",
"Etc/Universal|Universal",
"Etc/Universal|Zulu",

This is a quick fix

Better fix should include these changes:

• change findAndCreateLinks so that it does not depend on order of zones in unpacked array
• improve tests, add makeTestGuess for each timezone (it was missing for Etc/UTC)

I'll provide a better fix in a few days