Changed alloc_data to be a classic C array, instead of a vector.  Altered vector usage.
Per spec (enforced by MSVC++ debugging) I’ve learned that you cannot use [] to reference a spot in a vector that is beyond the ‘size()’ of the vector, even if it’s not beyond the ‘capacity()’ of the vector.
So, when my vector is empty, but has a reserve of 5, I cannot reference any of the first 5 points using [1] (etc) because that’s not in the C++ spec for vectors.
Because of this, my usage for alloc_data is thrown completely off, and my usage for the other variables (param_*) needed adjustment.  My solution to alloc_data was to use an old-school c-style array with realloc.  Since the typical use-case of this whole series is to never have to do re-allocations after initial allocation (hence, the constructor which takes a count to allocate all the memory ahead of time), this is trivially impacting on performance.
Main thing here, fix my bug in uvpg_connection_poll, which was me just not thinking, and not catching it before.
Additional: Tweaked checkQueuedRequests to not add more connections, as that seems a bit odd to do (if you make 10 requests, with 5 connections open, you have a decent chance of having 10+ connections open after that, because it would keep opening more when it finally gets a connection).