Test for expected return values when calling functions returning a success code (instead of discarding the return values).
Note to reviewers: The following commands can be used to verify that the only text fragments added in this PR are BOOST_CHECK(, ! and ) :
0$ git diff HEAD~1 | grep -E '^[\-][^\-]' | cut -b2- > before.txt
1$ git diff HEAD~1 | grep -E '^[\+][^\+]' | cut -b2- > after.txt
2$ cat after.txt | sed 's/BOOST_CHECK(//g' | sed 's/));/);/g' | tr -d '!' > after-sed.txt
3$ diff -u before.txt after-sed.txt
4$
