This will be used in the IPHC refactoring to control the reassembly buffer as a context. I also adapted the name of `gnrc_sixlowpan_frag_gc_rbuf()` to be in line with the rest of the newer functions.
This will be used in the IPHC refactoring to control the reassembly buffer as a context. I also adapted the name of `gnrc_sixlowpan_frag_gc_rbuf()` to be in line with the rest of the newer functions.