sigsegv, c-stack tests: Avoid test failures with ASAN. * tests/test-sigsegv-catch-stackoverflow1.c (HAVE_STACK_OVERFLOW_RECOVERY): Undefine if ASAN is enabled. * tests/test-sigsegv-catch-stackoverflow2.c (HAVE_STACK_OVERFLOW_RECOVERY): Likewise. * tests/test-c-stack.c (main): Skip the test if ASAN is enabled.