this constant is used for two test cases:
1. populate + interest /riot/text
-> static content has this=90 bytes size
2. appserver + interest /riot/appserver/test
-> dynamic content is created with exact
CCNL_RIOT_CHUNK_SIZE bytes
-> CCNL_RIOT_CHUNK_SIZE can be any value the
transceiver can handle
this buffer was used for two types of outgoing packets:
1. local msg
- msg can be big, there is is no apriori boundary -> use dynamic
memory instead
2. transceiver msg
- no need to copy msg in this buffer -> transceiver send is blocking
