Move the test apps to a subdirectory

hello/hello.c

@@ -0,0 +1,7 @@
+#define __USE_MINGW_ANSI_STDIO 1
+#include <stdio.h>
+
+int main(int argc, char* argv[]) {
+	printf("hello world! %f\n", 42.0);
+	return 0;
+}