Add signalfd() call to bionic.
Adding the signalfd call was done in 3 steps:
- add signalfd4 system call (function name and syscall
number) to libc/SYSCALLS.TXT
- generate all necessary headers by calling
libc/tools/gensyscalls.py. This patch is adding
the generated files since the build system
does not call gensyscalls.py.
- create the signalfd wrapper in signalfd.cpp and add
the function prototype to sys/signalfd.h
(cherry-pick of 0c11611c11, modified to
work with older versions of GCC still in use on some branches.)
Change-Id: I4c6c3f12199559af8be63f93a5336851b7e63355
