Otherwise, another user might recreate these files after the first
deletion. Particularly with temporary directories, this could result
in the removal of unintended files through symbol link attacks.
This is required to remove temporary directories which contain
temporary files. Previously, FIFO order meant that directory
removal was attempted when the directory still contained files,
which meant that temporary directory cleanup was essentially
unsupported.
The new test driver in <support/test-driver.c> has feature parity with
the old one. The main difference is that its hooking mechanism is
based on functions and function pointers instead of macros. This
commit also implements a new environment variable, TEST_COREDUMPS,
which disables the code which disables coredumps (that is, it enables
them if the invocation environment has not disabled them).
<test-skeleton.c> defines wrapper functions so that it is possible to
use existing macros with the new-style hook functionality.
This commit changes only a few test cases to the new test driver, to
make sure that it works as expected.
