Deprecated and Removed for 2020.04

Deprecated features during 2020.04 release cycle

gnrc_pktbuf: deprecate gnrc_pktbuf_replace_snip() (#13333)

By @miri64:

The function is unused and unneeded since #9484 and #5089 calls to provide unittests.

gnrc_nettype: deprecate IOVEC type (#13170)

By @miri64:

It is unused since #11193 and not expected to be re-used in the future.

gnrc/sixlowpan: add deprecation note for GNRC_SIXLOWPAN_FRAG_RBUF_AGGRESSIVE_OVERRIDE (#13129)

By @PeterKietzmann

When migrating configurations to Kconfig in #13123 we found that GNRC_SIXLOWPAN_FRAG_RBUF_AGGRESSIVE_OVERRIDE is a simple on/off switch which should be represented as a boolean. In Kconfig, a symbol is defined when enabled and it is not generated at all when disabled. In the latter case, the value would be set anyway in the config file :

#ifndef GNRC_SIXLOWPAN_FRAG_RBUF_AGGRESSIVE_OVERRIDE
#define GNRC_SIXLOWPAN_FRAG_RBUF_AGGRESSIVE_OVERRIDE    (1)
#endif

Offline we agreed with @jia200x and @leandrolanzieri that inverting the logic of the macro is the cleanest solution to this problem. As the semantics change, we changed the macro name and added a compile time error in case someone tries to use the old macro and we added a deprecation note to the documentation.

Removed features for 2020.04 release

net: Remove NHDP module (#13396)

Scheduled for removal by 2020.04 release in #11987, due to lack of maintenance.

pkg: Remove oonf_api (#13397)

Scheduled for removal by 2020.04 release in #12190 due to lack of users and maintenance.

gnrc_tftp: remove module (#12906)

Scheduled for removal in #11778 due to lack of maintenance.