Implemented (limited) Support for VATIN from Croatia

The support is "limited" because Croatian VATIN's also have a MOD
checksum which this is not checking.  Here we are considering the format
of the number (as processed by RegEx) to be sufficent.

In Regexp::Common::VATIN
  Added Pattern for HR (Croatia)

In t/01-basic.t
  Added test for Croatian sample VATIN