This commit adds APIS to create a ring buffer with specific memory caps. The
following APIs have been added:
- xRingbufferGetStaticBuffer()
- xRingbufferCreateWithCaps()
- vRingbufferDeleteWithCaps()
Ring buffers permit sending items of 0 size where:
- No-split/allow-split buffers will send an item (i.e., header) but the item
will have a 0 sized data section
- Byte buffers will simply return pdTRUE
This commit fixes an incorrect assert w.r.t 0 item size in
xRingbufferSendAcquire() and also adds a note to the API descriptions regarding
0 item sizes. A test case has also been added.
