src: add SIGINFO to supported signals

Though not a POSIX signal, SIGINFO is supported by BSD systems
(including Mac OS X) and is amongst the few signals that can be
triggered in a terminal via a simple key combination (CTRL-T).

On Linux, SIGINFO is an alias for SIGPWR; hence the defensive
conditionals in src/node.cc.

PR-URL: #6093
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

src/node.cc

@@ -692,6 +692,12 @@ const char *signo_string(int signo) {
 # endif
 #endif
 
+#ifdef SIGINFO
+# if !defined(SIGPWR) || SIGINFO != SIGPWR
+  SIGNO_CASE(SIGINFO);
+# endif
+#endif
+
 #ifdef SIGSYS
   SIGNO_CASE(SIGSYS);
 #endif

src/node_constants.cc

@@ -716,6 +716,10 @@ void DefineSignalConstants(Local<Object> target) {
   NODE_DEFINE_CONSTANT(target, SIGPWR);
 #endif
 
+#ifdef SIGINFO
+  NODE_DEFINE_CONSTANT(target, SIGINFO);
+#endif
+
 #ifdef SIGSYS
   NODE_DEFINE_CONSTANT(target, SIGSYS);
 #endif