long shared-memory-base-names could overflow a static internal buffer
and thus crash mysqld and various clients.  change both to dynamic
buffers, show everything but overflowing those buffers still works.

The test case for this would pretty much amount to
mysqld --shared-memory-base-name=HeyMrBaseNameXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX --shared-memory=1 &
mysqladmin --no-defaults --shared-memory-base-name=HeyMrBaseNameXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX shutdown

Unfortunately, we can't just use an .opt file for the
server. The .opt file is used at start-up, before any
include in the actual test can tell mysqltest to skip
this one on non-Windows. As a result, such a test would
break on unices.

Fixing mysql-test-run.pl to export full path for master
and slave would enable us to start a server from within
the test which is ugly and, what's more, doesn't work as
the server blocks (mysqltest offers no fire-and-forget
fork-and-exec), and mysqladmin never gets run.

Making the test rpl_windows_shm or some such so we can
is beyond ugly. As is introducing another file-name based
special case (run "win*.test" only when on Windows). As is
(yuck) coding half the test into mtr (as in, having it
hand out a customized environment conductive to the shm-
thing on Win only).

Situation is exacerbated by the fact that .sh is not
necessary run as expected on Win.

In short, it's just not worth it. No test-case until we
have a new-and-improved test framework.


sql-common/client.c:
  Bug#24924: shared-memory-base-name that is too long causes buffer overflow
  
  compose shared memory name in dynamic rather than static buffer to prevent
  overflows (clients)
sql/mysqld.cc:
  Bug#24924: shared-memory-base-name that is too long causes buffer overflow
  
  compose shared memory name in dynamic rather than static buffer to prevent
  overflows (server)