restructure and add ipi texs

ws2019/ipi/uebungen/cpp_headers/fibonacci.cc

@@ -0,0 +1,13 @@
+#include "fcpp.hh"
+
+int fib (int n)
+{
+  return cond( n==0, 0,
+	       cond( n==1, 1,
+		     fib(n-1)+fib(n-2) ) ); 
+}
+
+int main (int argc, char** argv)
+{
+  return print(fib(readarg_int(argc,argv,1)));
+}