libobs: Add win32 crash handler

A slightly refactored version of R1CH's crash handler, allows crash
handling for windows which provides stack traces of all threads and a
list of all loaded modules.  Also shows the processor, windows version,
and current libobs version.

libobs/obs.c

@@ -587,6 +587,10 @@ static bool obs_init(const char *locale)
 	return true;
 }
 
+#ifdef _WIN32
+extern void initialize_crash_handler(void);
+#endif
+
 bool obs_startup(const char *locale)
 {
 	bool success;
@@ -596,6 +600,10 @@ bool obs_startup(const char *locale)
 		return false;
 	}
 
+#ifdef _WIN32
+	initialize_crash_handler();
+#endif
+
 	success = obs_init(locale);
 	if (!success)
 		obs_shutdown();