previously failure to save the signal mask was not being caught due to
the uninitialized buffer containing zero bits (by chance).

this will be useful for testing libc ports to new targets where the
asm could be buggy/broken.

these tests will help detect wrong-macro-value errors on ports: things
like mismatch between stream/dgram and udp/tcp values, as well as
socket option settings.

this is mainly to test for incorrect macro/struct definitions