set FD_SETSIZE to 1024 on mingw

Sets FD_SETSIZE to 1024 under mingw systems, increasing it from the default of 64, and brings it into line with the previous limit for CMake builds on mingw.

configure.ac

@@ -265,6 +265,9 @@ case "${host_os}" in
         if test "x$enable_static" = "xyes"; then
             AC_MSG_ERROR([Building static libraries is not supported under MinGW32])
         fi
+        
+		# Additional for windows to set FD_SETSIZE to a larger number
+		CPPFLAGS=" -DFD_SETSIZE=1024 $CPPFLAGS"
         ;;
     *cygwin*)
         # Define on Cygwin to enable all library features