signal: show Windows popup window on crash (#410)

## Link to GitHub Issue, if one exists
#345 

## Description of change
Show a MessageBox when signal detects a crash.

## Testing
Tested full screen and windowed games.

src/spice2x/util/deferlog.cpp

@@ -72,4 +72,25 @@ namespace deferredlogs {
             log_warning("troubleshooter", "{}", msg);
         });
     }
+
+    void show_popup_for_crash() {
+        static std::once_flag shown;
+        std::call_once(shown, []() {
+            const std::string title = "spice2x (" + to_string(VERSION_STRING_CFG) + ") - crash handler";
+            std::string text;
+            text += "Game has crashed.\n\n";
+            text += "Check log.txt and look for error messages near the end of file.\n\n";
+            text += "Unsure what to do next?\n";
+            text += "  * update spice2x to the latest version\n";
+            text += "  * check the FAQ on spice2x wiki on github\n";
+            text += "  * do NOT screenshot this, instead, share log.txt with someone and ask for help\n\n";
+            text += "Press Enter, Esc, Alt+F4, or click OK to exit. Otherwise, game will close in 30 seconds.";
+
+            MessageBox(
+                nullptr,
+                text.c_str(),
+                title.c_str(),
+                MB_OK | MB_ICONERROR | MB_TASKMODAL | MB_SETFOREGROUND | MB_TOPMOST);
+        });
+    }
 }

src/spice2x/util/deferlog.h

@@ -11,4 +11,5 @@ namespace deferredlogs {
 
     void defer_error_messages(std::initializer_list<std::string> messages);
     void dump_to_logger(bool is_crash=false);
+    void show_popup_for_crash();
 }

src/spice2x/util/logging.cpp

@@ -1,5 +1,7 @@
 #include "logging.h"
 
+DWORD LOG_FATAL_SLEEP = 10000;
+
 std::string_view log_get_datetime() {
     return log_get_datetime(time(nullptr));
 }

src/spice2x/util/logging.h

@@ -71,6 +71,8 @@ struct fmt::formatter<fmt_hresult> {
     }
 };
 
+extern DWORD LOG_FATAL_SLEEP;
+
 // misc log
 #define LOG_FORMAT(level, module, fmt_str, ...) fmt::format(FMT_COMPILE("{}" fmt_str "\n"), \
     fmt_log { std::time(nullptr), level, module }, ## __VA_ARGS__)
@@ -84,7 +86,7 @@ struct fmt::formatter<fmt_hresult> {
     logger::push(LOG_FORMAT("F", module, format_str, ## __VA_ARGS__), logger::Style::RED); \
     logger::push(LOG_FORMAT("F", "spice", "encountered a fatal error, you can close the window or press ctrl + c"), logger::Style::RED); \
     launcher::stop_subsystems(); \
-    Sleep(10000); \
+    Sleep(LOG_FATAL_SLEEP); \
     launcher::kill(); \
     std::terminate(); \
 } ((void) 0 )