* mmap.cc (mlock): Add standard syscall return value debugging output.

* mmap.cc (mlock): Add standard syscall return value debugging output.
(munlock): Ditto.
(posix_madvise): Ditto.
* signal.cc: Remove obsolete sigcatchers stuff throughout.
(sigaction_worker): Add function name parameter and use it to show standard
syscall return value debugging output.  Also add fault protection.
(sigaction): Accommodate extra argument to sigaction_worker.
(siginterrupt): Ditto.
* syscalls.cc (read): Remove obsolete sigcatchers stuff.
(readv): Ditto.