Re-work best_access_path() and find_best() to reuse E(#rows(range access)) as
E(#rows(ref[_or_null](const) access) only when it is appropriate.
[This is the final cumulative patch]


mysql-test/r/select.result:
  BUG#17379: Testcase
mysql-test/r/subselect.result:
  BUG#17379: Updated test results
mysql-test/t/select.test:
  BUG#17379: Testcase
sql/opt_range.cc:
  BUG#17379: Wrong reuse of E(#rows(range)) as E(#rows(ref(const))):
  Make range optimizer together with TABLE::quick_* also return TABLE::quick_n_ranges
sql/sql_select.cc:
  BUG#17379: Wrong reuse of E(#rows(range)) as E(#rows(ref(const))):
  Re-work best_access_path() to reuse E(#rows(range access)) as
  E(#rows(ref[_or_null](const) access) only when it is appropriate.
sql/table.h:
  BUG#17379: Wrong reuse of E(#rows(range)) as E(#rows(ref(const))):
  Make range optimizer together with TABLE::quick_* also return TABLE::quick_n_ranges