Based on tewinget's update.
Make OpenAlias address format independent of existing DNS functions.
Add tests.
Test:
make debug-test
cd build/debug/tests/unit_tests
# test that regular DNS functions work, including IPv4 lookups.
# also test function that converts OpenAlias address format
make && ./unit_tests --gtest_filter=DNSResolver*
# test that OpenAlias addresses like donate@getmonero.org work from
# wallet tools
make && ./unit_tests --gtest_filter=AddressFromURL.Success
DNSSEC is now implemented with the hardcoded key from unbound.
This will need to be not hardcoded in the future, but is okay for now.
Unit tests updated for DNSSEC (as well as for the fact that, contrary to
previous assumption, example.com does not have a static IP address).
Note: DNSResolver does not yet *use* DNSSEC, but rather this commit is
preparation for including DNSSEC validation. The function in
src/wallet/wallet2.cpp that uses DNSResolver still needs its parameters
updated accordingly.
