What: Eliminate the "descriptor" argument from sendi functions.
Why: The only thing this argument is used for is so that the sendi function can allocate a descriptor in the event that the "send" cannot complete. But, in that case, the sendi reverts to the PML, where there is already code to allocate a descriptor. So, each sendi function (in each BTL that has a sendi function) must have code that is already in the PML anyhow. This is unnecessary extra coding and not clean design.
Where: In each BTL that has a sendi function (only three, and there are not all used) and in the function prototype and at the PML calling site.
When: I'd like to incorporate this in the shared-memory latency work I'm doing that we're targetting for 1.3.x.
Timeout: Feb 27.
