This is simpler and more flexible than embedding C code in the Ruby options
(:suite_setup and :suite_teardown).  However, support for :suite_setup and
:suite_teardown is kept for backwards compatibility.

Several configurations are possible:
1. :suite_setup and :suite_teardown options provided and used.
2. :suite_setup and :suite_teardown options not provided (nil):
  2a. Weak symbols not supported; suiteSetUp() and suiteTearDown() are not called.
      It would be simpler to make user-provided functions mandatory in this case,
      but it could break some pre-existing test suites.
  2b. Weak symbols are supported and the stub implementations of suiteSetUp() and
      suiteTearDown() are called if there are no user-provided functions.
  2c. Weak symbols are supported but overridden by user-provided suiteSetUp() and
      suiteTearDown() functions.