Hack to add pthread to link libraries on mingw

This should link winpthreads.  We really shouldn't be passing these this
way, but that seems to be the existing solution, and it works for now.

CMakeLists.txt

@@ -150,11 +150,11 @@ if((${Boost_MAJOR_VERSION} EQUAL 1) AND (${Boost_MINOR_VERSION} EQUAL 54))
 endif()
 include_directories(SYSTEM ${Boost_INCLUDE_DIRS})
 if(MINGW)
-  set(Boost_LIBRARIES "${Boost_LIBRARIES};ws2_32;mswsock")
+  set(Boost_LIBRARIES "${Boost_LIBRARIES};pthread;mswsock;ws2_32")
 elseif(APPLE OR FREEBSD)
   set(Boost_LIBRARIES "${Boost_LIBRARIES}")
 elseif(NOT MSVC)
-  set(Boost_LIBRARIES "${Boost_LIBRARIES};rt;pthread")
+  #set(Boost_LIBRARIES "${Boost_LIBRARIES};rt;pthread")
 endif()
 
 file(MAKE_DIRECTORY "${CMAKE_BINARY_DIR}/version")