Add missing include for raise(3)
If SIGTRAP is defined, this file may end up using raise(3), which is
defined in csignal, leading to a compilation failure on at least
OpenBSD/sparc64 with gcc 8.
diff --git a/googletest/src/gtest.cc b/googletest/src/gtest.cc
index 99b22ed..dcf4e26 100644
--- a/googletest/src/gtest.cc
+++ b/googletest/src/gtest.cc
@@ -43,6 +43,7 @@
#include <algorithm>
#include <chrono> // NOLINT
#include <cmath>
+#include <csignal>
#include <cstdint>
#include <cstdlib>
#include <cstring>
