check for and handle syscall failure in all intercepted syscalls

_From [derek.br...@gmail.com](https://code.google.com/u/117968039472581148324/) on May 28, 2009 10:00:33_

while we do handle failure in the various mmap/mprotect syscalls we don't
for signal-related syscalls like SYS_rt_sigaction and SYS_rt_sigprocmask.
this Issue covers going through all of the intercepted syscalls and making
sure we're checking for and properly handling failure.

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=148_