We have f_inet_ntoa() for converting IPv4 addresses to strings,
but so far there was no similar function for IPv6 addresses.
Change-Id: I0858cf8cb44a6673e19f3496c362d68fcdd7b18d
TTCN-3 interestingly doens't seem to have any case-insensitive string
matching or functions to convert to uppwer/lowercase.
Change-Id: I2e6e0fd2da001a3cc6d9c31c9e766ae54bf17b2f