This is a collection of examples of how to use the Idris FFI.
We have a C library testlib with a function int foo(int); that takes an int,
adds 1 to the argument and returns the result. The Idris program calls foo with
42 as argument and then prints the result.
We have two functions that return a char pointer. One of them will always
return a C-string while the other always returns NULL. Note that the example
doesn't work in v0.9.9.2.