Lint: primarily make sure no WiredTiger call that returns an error value
ignores that error.
We're setting "home" to NULL, and then using it in error messages, which
isn't good, we'll drop core if they ever fire, not a good thing in a
sample program.  Add boilerplate to the examples, if we don't have an
evironment specified by "make check", create a clean standard one and
use it.
Merge branch 'develop' into log-printf
Merge branch 'log-printf' into log-printf-docs
Switch ex_log to the new develop branch's naming for home directories,
update the Makefile so "make clean" works.