fix: add qualified capi lua descriptor alias - #16

The release that closes mcpplibs/tinyhttps#15 (a socket whose body was not read
to the end went back into the connection pool, and the next request read the
leftovers as its status line) and #16 (a write to a departed peer killed the
host process with SIGPIPE). Eleven pool-invariant defects in total; the issue
named two of them.

Descriptor: three platform tables, GLOBAL and CN, sha256
acb4d494bae2030632f4d91e4e8420cee9aed4560e4d0a6876e85232d2ba67f9. The GitHub
archive was downloaded twice independently and both copies carried that digest;
the CN mirror was uploaded from the first of them and a fresh CN download is
byte-identical. `mcpp test` was run against BOTH mirrors from a cleared cache,
and each reported `Downloading mcpplibs.tinyhttps v0.3.0` and produced an
archive with the same digest — so neither URL is recorded on the strength of the
other.

The smoke example moves to 0.3.0 and gains three assertions, chosen because they
are the ones a version bump could break rather than because they are new:

  * `parse_status_line` accepts `HTTP/1.1 200 OK` and REJECTS
    `BBBB 999 XHTTP/1.1 200 OK`, which is the exact input from the issue — every
    reader used to take the first run of digits it found and report an ordinary
    999.
  * `response.bodyComplete` and `bodyError`, the new fields, hold their
    documented defaults.
  * `HttpResponse{204, "No Content", {}, {}}` still compiles. That line is
    unchanged from the 0.2.9 example and is the whole compatibility claim for
    0.3.0's added fields: they are appended, so a four-initialiser aggregate
    initialisation keeps working and `ok()` keeps meaning what it meant.