Add a ->modules_loaded member to struct test, which is a comma-separated
list of modules that should be present after the test finishes. Both
missing and excess modules cause an error.
Also define noreturn w/o <stdnoreturn.h> and move it to macro.h instead
of in the testsuite.
Based on similar commit on systemd by Shawn Landden
<shawn@churchofgit.com>.
Functions that always call exit() should be marked with attribute
noreturn. With glibc this is not necessary, but it fails to compile with
uClibc otherwise.
