Allow disabling signal handling, turn signal handling off by default.

src/SignalHandling.cpp

@@ -1,6 +1,6 @@
 #include "SignalHandling.hpp"
 
-#if !WINDOWS
+#if !WINDOWS && SIGNAL_HANDLING
 /// \cond SKIP
 void (*ArbUt::SignalHandling::_callback)(const char*) = nullptr;
 /// \endcond

src/SignalHandling.hpp

@@ -1,5 +1,6 @@
 #ifndef ARBUTILS_SIGNALHANDLING_HPP
 #define ARBUTILS_SIGNALHANDLING_HPP
+#if SIGNAL_HANDLING
 #if PRETTYTRACES && !WINDOWS
 #define BACKWARD_HAS_DW 1
 #include "../extern/backward.hpp"
@@ -176,4 +177,5 @@ namespace ArbUt {
 /// @fn ArbUt::SignalHandling::loaded()
 /// @brief Whether or not the signal handler is loaded
 
+#endif // SIGNAL_HANDLING
 #endif // ARBUTILS_SIGNALHANDLING_HPP