With gcc-4.9.4 libstdc++ std::min() is not a constexpr as required
by c++14 conforming compilers. Replace std::min with a conditional.

--- src/devices/video/poly.h	2016-08-31 03:47:01.000000000 +0200
+++ src/devices/video/poly.h	2016-08-31 07:56:47.483694756 +0200
@@ -224,7 +224,7 @@
 	// internal array types
 	typedef poly_array<polygon_info, _MaxPolys> polygon_array;
 	typedef poly_array<_ObjectData, _MaxPolys + 1> objectdata_array;
-	typedef poly_array<work_unit, std::min(_MaxPolys * UNITS_PER_POLY, 65535)> unit_array;
+	typedef poly_array<work_unit, (_MaxPolys * UNITS_PER_POLY < 65535 ? _MaxPolys * UNITS_PER_POLY : 65535)> unit_array;
 
 	// round in a cross-platform consistent manner
 	inline INT32 round_coordinate(_BaseType value)