[FS#1381] busybox: Enable ip_tunnel and ip_neighbor by default

[LEDE Bugs]

The following task has a new comment added:

FS#1381 - busybox: Enable ip_tunnel and ip_neighbor by default
User who did this - Jeff Kletsky (jeffsf)

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Closing this as even with CONFIG_BUSYBOX_CONFIG_FEATURE_IP_TUNNEL=y busybox apparently doesn't support gretap.

https://forum.lede-project.org/t/solved-busybox-doesnt-support-gretap/12032
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1381#comment4389