Previous naming is misleading, as it seems to indicate the function is
used to generate any kind of message, which is wrong.
Change-Id: Ib0228c64bbf104accdbbebb6076004a6a1f44c6f
Move code from message_handling containing both code for generic
cbc_message and specific cbsp_message into thers files. The former are
moved to cbc_message.c and the later to cbsp_msg.c, similar to what's
already done for SBc-AP messages.
Change-Id: Ie4082e40f23170cfd6c573fbbb7beb8c6226b6e6