gnrc_sock: make sock compilable with gnrc_neterr
gnrc_sock: make sock compilable with gnrc_neterr

gnrc_sock currently does not compile with `gnrc_neterr` included, since
both `msg_try_receive()` and `msg_try_send()` expect a *pointer* to a
`msg_t`, not a `msg_t`.

To test, just compile an application using `gnrc_sock` (e.g.
`examples/gcoap`) with `USEMODULE+=gnrc_neterr`.

josephnoir/RIOT,neiljay/RIOT,BytesGalore/RIOT,toonst/RIOT,aeneby/RIOT,smlng/RIOT,aeneby/RIOT,OTAkeys/RIOT,BytesGalore/RIOT,ant9000/RIOT,aeneby/RIOT,neiljay/RIOT,lazytech-org/RIOT,smlng/RIOT,mtausig/RIOT,yogo1212/RIOT,jasonatran/RIOT,LudwigKnuepfer/RIOT,mtausig/RIOT,gebart/RIOT,kbumsik/RIOT,rfuentess/RIOT,toonst/RIOT,yogo1212/RIOT,LudwigKnuepfer/RIOT,x3ro/RIOT,biboc/RIOT,kaspar030/RIOT,smlng/RIOT,kaspar030/RIOT,OlegHahm/RIOT,authmillenon/RIOT,avmelnikoff/RIOT,basilfx/RIOT,OlegHahm/RIOT,kaspar030/RIOT,LudwigOrtmann/RIOT,smlng/RIOT,jasonatran/RIOT,ant9000/RIOT,kYc0o/RIOT,yogo1212/RIOT,gebart/RIOT,A-Paul/RIOT,OTAkeys/RIOT,biboc/RIOT,josephnoir/RIOT,x3ro/RIOT,avmelnikoff/RIOT,jasonatran/RIOT,gebart/RIOT,mtausig/RIOT,BytesGalore/RIOT,A-Paul/RIOT,kbumsik/RIOT,authmillenon/RIOT,cladmi/RIOT,x3ro/RIOT,toonst/RIOT,x3ro/RIOT,biboc/RIOT,miri64/RIOT,biboc/RIOT,x3ro/RIOT,josephnoir/RIOT,cladmi/RIOT,toonst/RIOT,RIOT-OS/RIOT,rfuentess/RIOT,gebart/RIOT,ant9000/RIOT,ant9000/RIOT,OTAkeys/RIOT,mfrey/RIOT,OlegHahm/RIOT,josephnoir/RIOT,yogo1212/RIOT,authmillenon/RIOT,toonst/RIOT,mtausig/RIOT,LudwigKnuepfer/RIOT,josephnoir/RIOT,authmillenon/RIOT,neiljay/RIOT,OTAkeys/RIOT,kaspar030/RIOT,avmelnikoff/RIOT,LudwigOrtmann/RIOT,mfrey/RIOT,lazytech-org/RIOT,basilfx/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,cladmi/RIOT,aeneby/RIOT,gebart/RIOT,A-Paul/RIOT,RIOT-OS/RIOT,kbumsik/RIOT,rfuentess/RIOT,RIOT-OS/RIOT,neiljay/RIOT,basilfx/RIOT,kbumsik/RIOT,A-Paul/RIOT,mfrey/RIOT,lazytech-org/RIOT,LudwigKnuepfer/RIOT,basilfx/RIOT,LudwigKnuepfer/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,BytesGalore/RIOT,avmelnikoff/RIOT,miri64/RIOT,A-Paul/RIOT,LudwigOrtmann/RIOT,lazytech-org/RIOT,OTAkeys/RIOT,biboc/RIOT,lazytech-org/RIOT,kbumsik/RIOT,LudwigOrtmann/RIOT,LudwigOrtmann/RIOT,OlegHahm/RIOT,mfrey/RIOT,miri64/RIOT,aeneby/RIOT,mfrey/RIOT,cladmi/RIOT,kYc0o/RIOT,LudwigOrtmann/RIOT,kaspar030/RIOT,cladmi/RIOT,smlng/RIOT,jasonatran/RIOT,jasonatran/RIOT,yogo1212/RIOT,miri64/RIOT,OlegHahm/RIOT,basilfx/RIOT,authmillenon/RIOT,BytesGalore/RIOT,mtausig/RIOT,neiljay/RIOT,rfuentess/RIOT,avmelnikoff/RIOT,ant9000/RIOT,yogo1212/RIOT,kYc0o/RIOT,miri64/RIOT,rfuentess/RIOT,kYc0o/RIOT