980e4ee89a
This is true:
-1 > 1u
because the integer literal `-1` is first converted to a large unsigned
value and then compared to the unsigned `1`.
This patch fixes several of those isses in the farthest insertion
algorithm.
`-Wsign-compare` catches those issues.
References:
- http://stackoverflow.com/a/5416498
- C++14 standard