[committed] remove multi-range selftests from range-ops.cc
Multi-range selftests are unused, as we don't currently have them on
trunk. This was leftover from the original ranger branch. Removing
them has the added benefit that the selftests no longer need to peek at
m_max_pairs, so value_range no longer needs to friend the selftests.
This tidies up the selftest.h header file, and allows us to put the
range tests in the correct namespace.