Integrated Chrome tracing

Added support for chrome tracing by integrating the
minitrace library (github.com/hrydgard/minitrace),
and modified it with a background flushing thread that allows
tracing to continue automatically after the predefined
1 million event limit.

Menu items and an accelerator (Ctr+T) have also been
added. Starting and stopping the trace simply replaces
trace.json with the new trace data.

The feature is disabled by default. Pass MINITRACE=y
to the build command to enable it. Some traces are
already added as an example, however they won't have
any effect if the feature is disabled.

src/win/win.c

@@ -49,7 +49,9 @@
 #include <86box/win_sdl.h>
 #include <86box/win.h>
 #include <86box/version.h>
-
+#ifdef MTR_ENABLED
+#include <minitrace/minitrace.h>
+#endif
 
 typedef struct {
     WCHAR str[512];
@@ -217,6 +219,21 @@ plat_get_string(int i)
     return((wchar_t *)str);
 }
 
+#ifdef MTR_ENABLED
+void
+init_trace(void)
+{
+    mtr_init("trace.json");
+    mtr_start();
+}
+
+void
+shutdown_trace(void)
+{
+    mtr_stop();
+    mtr_shutdown();
+}
+#endif
 
 /* Create a console if we don't already have one. */
 static void