net: lwip: add wget command

Add support for the wget command with NET_LWIP. The command normally
expects a URL: wget [loadaddr] url, but it also accepts the legacy
syntax: wget [loadaddr] [server:]file.
The server IP may alternatively be supplied via ${httpserverip} which
has higher priority than ${serverip}.

Based on code initially developed by Maxim U.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Co-developed-by: Maxim Uvarov <muvarov@gmail.com>
Cc: Maxim Uvarov <muvarov@gmail.com>
Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/net/lwip/Makefile b/net/lwip/Makefile
index 645d8a8..f2558f8 100644
--- a/net/lwip/Makefile
+++ b/net/lwip/Makefile
@@ -5,3 +5,4 @@
 obj-$(CONFIG_CMD_DNS) += dns.o
 obj-$(CONFIG_CMD_PING) += ping.o
 obj-$(CONFIG_CMD_TFTPBOOT) += tftp.o
+obj-$(CONFIG_CMD_WGET) += wget.o