Retire FORCE_INLINE

No speed regression on my machine (i7-3770k, gcc 4.9.1, linux 3.16):

        stat        test     master   diff
        mean   2,482,415  2,474,987  7,906
        stdev      4,603      5,644  2,497

        speedup        0.32%
        P(speedup>0)  100.0%

Fishtest 9+0.03:

ELO: 0.26 +-1.8 (95%) LOS: 61.2%
Total: 60000 W: 12437 L: 12392 D: 35171

No functional change.

Resolves #334

src/movepick.cpp

@@ -52,7 +52,7 @@ namespace {
   // pick_best() finds the best move in the range (begin, end) and moves it to
   // the front. It's faster than sorting all the moves in advance when there
   // are few moves e.g. the possible captures.
-  inline Move pick_best(ExtMove* begin, ExtMove* end)
+  Move pick_best(ExtMove* begin, ExtMove* end)
   {
       std::swap(*begin, *std::max_element(begin, end));
       return *begin;