Changes to correct TCP write buffereing build errors

include/nuttx/net/net.h

include/nuttx/net/uip/uip-tcp.h

net/Kconfig

net/Makefile

net/net_close.c

net/net_send_buffered.c

net/recvfrom.c

net/setsockopt.c

net/socket.c

net/uip/Make.defs

net/uip/uip_initialize.c

net/uip/uip_internal.h

net/uip/uip_tcpcallback.c

net/uip/uip_tcpconn.c

net/uip/uip_tcpreadahead.c

net/uip/uip_tcpwrbuffer.c