LibC: Implement {sig,_,}{longjmp,setjmp}

userspace/tests/test-setjmp/main.cpp

@@ -0,0 +1,22 @@
+#include <setjmp.h>
+#include <stdio.h>
+
+jmp_buf env;
+
+void iterate()
+{
+	static volatile int count = 0;
+	if (count < 10)
+	{
+		count = count + 1;
+		longjmp(env, count);
+	}
+}
+
+int main()
+{
+	printf("start\n");
+	if (int ret = setjmp(env))
+		printf("longjmp %d\n", ret);
+	iterate();
+}