Comment 11 for bug 1722376

OK, I more-less implemented it, but it does not compile because of this:
http://bazaar.launchpad.net/~widelands-dev/widelands/ai_small_requests/view/head:/src/ai/defaultai.cc#L1964

/var/widelands2/BZR/ai_small_requests/src/ai/defaultai.cc: In member function ‘bool
DefaultAI::construct_building(uint32_t)’:
/var/widelands2/BZR/ai_small_requests/src/ai/defaultai.cc:1963:50: error: passing ‘const Widelands::Map’ as ‘this’
argument discards qualifiers [-fpermissive]
  const bool seafaring_map = map.allows_seafaring();

Please advice how to do it....