A gcc_jit_param represents a parameter to a function.
In preparation for creating a function, create a new parameter of the given type and name.
The parameter type
must be non-void.
The parameter name
must be non-NULL. The call takes a copy of the
underlying string, so it is valid to pass in a pointer to an on-stack
buffer.
Parameters are lvalues, and thus are also rvalues (and objects), so the following upcasts are available:
Upcasting from param to lvalue.
Upcasting from param to rvalue.
Upcasting from param to object.