dist/tools/ethos: Build escaped packet in buffer before writing to UART
dist/tools/ethos: Build escaped packet in buffer before writing to UART

Significantly improves throughput and latency on FRDM-KW41Z.

Ping with a packet of size 100 yields a 30 ms roundtrip with this
patch, 177 ms without. Size 1000 ping before: 1160 ms, after: 188 ms

beurdouche/RIOT,kerneltask/RIOT,x3ro/RIOT,mtausig/RIOT,LudwigKnuepfer/RIOT,LudwigOrtmann/RIOT,OlegHahm/RIOT,BytesGalore/RIOT,biboc/RIOT,rfuentess/RIOT,kbumsik/RIOT,OTAkeys/RIOT,kaspar030/RIOT,immesys/RiSyn,A-Paul/RIOT,yogo1212/RIOT,mtausig/RIOT,immesys/RiSyn,josephnoir/RIOT,cladmi/RIOT,yogo1212/RIOT,mfrey/RIOT,LudwigKnuepfer/RIOT,roberthartung/RIOT,rfuentess/RIOT,adrianghc/RIOT,gebart/RIOT,Josar/RIOT,kerneltask/RIOT,avmelnikoff/RIOT,kYc0o/RIOT,LudwigOrtmann/RIOT,beurdouche/RIOT,ks156/RIOT,Josar/RIOT,ant9000/RIOT,kbumsik/RIOT,BytesGalore/RIOT,yogo1212/RIOT,ks156/RIOT,OTAkeys/RIOT,ks156/RIOT,plushvoxel/RIOT,basilfx/RIOT,kYc0o/RIOT,kaspar030/RIOT,kYc0o/RIOT,immesys/RiSyn,authmillenon/RIOT,smlng/RIOT,kerneltask/RIOT,aeneby/RIOT,neiljay/RIOT,LudwigOrtmann/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,hamilton-mote/RIOT-OS,plushvoxel/RIOT,adjih/RIOT,x3ro/RIOT,miri64/RIOT,beurdouche/RIOT,kaspar030/RIOT,LudwigKnuepfer/RIOT,hamilton-mote/RIOT-OS,avmelnikoff/RIOT,ant9000/RIOT,josephnoir/RIOT,cladmi/RIOT,roberthartung/RIOT,authmillenon/RIOT,aeneby/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,BytesGalore/RIOT,plushvoxel/RIOT,adjih/RIOT,miri64/RIOT,Josar/RIOT,roberthartung/RIOT,yogo1212/RIOT,aeneby/RIOT,ant9000/RIOT,BytesGalore/RIOT,lazytech-org/RIOT,gebart/RIOT,biboc/RIOT,neiljay/RIOT,cladmi/RIOT,basilfx/RIOT,LudwigKnuepfer/RIOT,josephnoir/RIOT,authmillenon/RIOT,cladmi/RIOT,yogo1212/RIOT,toonst/RIOT,BytesGalore/RIOT,Josar/RIOT,josephnoir/RIOT,toonst/RIOT,RIOT-OS/RIOT,neiljay/RIOT,jasonatran/RIOT,x3ro/RIOT,plushvoxel/RIOT,adrianghc/RIOT,beurdouche/RIOT,rfuentess/RIOT,A-Paul/RIOT,ks156/RIOT,kbumsik/RIOT,mfrey/RIOT,neiljay/RIOT,neiljay/RIOT,authmillenon/RIOT,OTAkeys/RIOT,avmelnikoff/RIOT,beurdouche/RIOT,lazytech-org/RIOT,ks156/RIOT,josephnoir/RIOT,lazytech-org/RIOT,mfrey/RIOT,mfrey/RIOT,jasonatran/RIOT,jasonatran/RIOT,kbumsik/RIOT,hamilton-mote/RIOT-OS,immesys/RiSyn,biboc/RIOT,LudwigOrtmann/RIOT,adjih/RIOT,adjih/RIOT,ant9000/RIOT,ant9000/RIOT,RIOT-OS/RIOT,gebart/RIOT,lazytech-org/RIOT,adrianghc/RIOT,gebart/RIOT,avmelnikoff/RIOT,biboc/RIOT,smlng/RIOT,OlegHahm/RIOT,LudwigKnuepfer/RIOT,miri64/RIOT,miri64/RIOT,toonst/RIOT,immesys/RiSyn,basilfx/RIOT,RIOT-OS/RIOT,rfuentess/RIOT,kYc0o/RIOT,biboc/RIOT,x3ro/RIOT,smlng/RIOT,LudwigOrtmann/RIOT,A-Paul/RIOT,adrianghc/RIOT,cladmi/RIOT,aeneby/RIOT,OlegHahm/RIOT,aeneby/RIOT,mtausig/RIOT,mtausig/RIOT,jasonatran/RIOT,OTAkeys/RIOT,gebart/RIOT,immesys/RiSyn,kerneltask/RIOT,kerneltask/RIOT,authmillenon/RIOT,adrianghc/RIOT,hamilton-mote/RIOT-OS,hamilton-mote/RIOT-OS,OTAkeys/RIOT,LudwigOrtmann/RIOT,OlegHahm/RIOT,kYc0o/RIOT,mfrey/RIOT,x3ro/RIOT,toonst/RIOT,basilfx/RIOT,A-Paul/RIOT,A-Paul/RIOT,avmelnikoff/RIOT,mtausig/RIOT,jasonatran/RIOT,miri64/RIOT,plushvoxel/RIOT,OlegHahm/RIOT,basilfx/RIOT,lazytech-org/RIOT,toonst/RIOT,kbumsik/RIOT,roberthartung/RIOT,yogo1212/RIOT,roberthartung/RIOT,smlng/RIOT,rfuentess/RIOT,adjih/RIOT,smlng/RIOT,Josar/RIOT,kaspar030/RIOT