* libc/sys/linux/Makefile.am: Add sig.c and sigaction.c. Also
make siglist.inc dependent on sig.c instead of signal.c.
* libc/sys/linux/Makefile.in: Regenerated.
* libc/sys/linux/sig.c: Rename from signal.c and change code to
use NSIG instead of _NSIG.
* libc/sys/linux/sigaction.c: New file.
* libc/sys/linux/signal.c: Changed to be linux signal() function
so as to override regular newlib default signal.c.
* libc/sys/linux/linuxthreads/config.h: Add __ASSUME_REALTIME_SIGNALS
definition.
* libc/sys/linux/linuxthreads/testrtsig.h: New file.
* libc/sys/linux/machine/i386/Makefile.am: Remove sigset.c.
* libc/sys/linux/machine/i386/Makefile.in: Regenerated.
* libc/sys/linux/machine/i386/sigset.c: Moved to linux main directory.
* libc/sys/linux/sigset.c: Moved from machine/i386 directory.
* libc/sys/linux/sys/signal.h: Redefine NSIG to _NSIG and override
default linux sigset_t typedef by defining it equal to __sigset_t.
* libc/unix/sigset.c: Add check so code isn't compiled on systems
with a sigset_t that isn't implemented with a single int.