Adding cython v0.20.2 in third-party.

third_party/cython/src/Cython/Includes/libc/signal.pxd

Index: third_party/cython/src/Cython/Includes/libc/signal.pxd
diff --git a/third_party/cython/src/Cython/Includes/libc/signal.pxd b/third_party/cython/src/Cython/Includes/libc/signal.pxd
new file mode 100644
index 0000000000000000000000000000000000000000..08d2ebfad0bd651e8ef8ef819f6c5f0b83544c52
--- /dev/null
+++ b/third_party/cython/src/Cython/Includes/libc/signal.pxd
@@ -0,0 +1,68 @@
+# 7.14 Signal handling <signal.h>
+
+ctypedef void (*sighandler_t)(int SIGNUM) nogil
+
+cdef extern from "signal.h" nogil:
+
+    ctypedef int sig_atomic_t
+
+    enum: SIGABRT
+    enum: SIGFPE
+    enum: SIGILL
+    enum: SIGINT
+    enum: SIGSEGV
+    enum: SIGTERM
+
+    sighandler_t SIG_DFL
+    sighandler_t SIG_IGN
+    sighandler_t SIG_ERR
+
+    sighandler_t signal        (int signum, sighandler_t action)
+    int          raise_"raise" (int signum)
+
+
+cdef extern from "signal.h" nogil:
+
+    # Program Error
+    enum: SIGFPE
+    enum: SIGILL
+    enum: SIGSEGV
+    enum: SIGBUS
+    enum: SIGABRT
+    enum: SIGIOT
+    enum: SIGTRAP
+    enum: SIGEMT
+    enum: SIGSYS
+    # Termination
+    enum: SIGTERM
+    enum: SIGINT
+    enum: SIGQUIT
+    enum: SIGKILL
+    enum: SIGHUP
+    # Alarm
+    enum: SIGALRM
+    enum: SIGVTALRM
+    enum: SIGPROF
+    # Asynchronous I/O
+    enum: SIGIO
+    enum: SIGURG
+    enum: SIGPOLL
+    # Job Control
+    enum: SIGCHLD
+    enum: SIGCLD
+    enum: SIGCONT
+    enum: SIGSTOP
+    enum: SIGTSTP
+    enum: SIGTTIN
+    enum: SIGTTOU
+    # Operation Error
+    enum: SIGPIPE
+    enum: SIGLOST
+    enum: SIGXCPU
+    enum: SIGXFSZ
+    # Miscellaneous
+    enum: SIGUSR1
+    enum: SIGUSR2
+    enum: SIGWINCH
+    enum: SIGINFO
+