Fix API typos (#541)

doc/docs/NLopt_C-plus-plus_Reference.md

@@ -256,13 +256,13 @@ Algorithm-specific parameters
 
 Certain NLopt optimization algorithms allow you to specify additional parameters by calling
 ```
-nlopt_result nlopt::opt::set_param(const char *name, double val);
+void nlopt::opt::set_param(const char *name, double val);
 bool nlopt::opt::has_param(const char *name);
 double nlopt::opt::get_param(const char *name, double defaultval);
 unsigned nlopt::opt::num_params();
 const char *nlopt::opt::nth_param(unsigned n);
 ```
-where the string `name` is the name of an algorithm-specific parameter and `val` is the value you are setting the parameter to.   These functions are equivalent to the [C API](NLopt_Reference#algorithm-specific-parameters) functions of the corresponding names.
+where the string `name` is the name of an algorithm-specific parameter and `val` is the value you are setting the parameter to. These functions are equivalent to the [C API](NLopt_Reference#algorithm-specific-parameters) functions of the corresponding names.
 
 
 Performing the optimization

doc/docs/NLopt_Reference.md

@@ -310,11 +310,11 @@ Certain NLopt optimization algorithms allow you to specify additional parameters
 nlopt_result nlopt_set_param(nlopt_opt opt, const char *name, double val);
 ```
 
-where the string `name` is the name of an algorithm-specific parameter and `val` is the value you are setting the parameter to.   For example, the MMA algorithm has a parameter `"inner_maxeval"`, an upper bound on the number of "inner" iterations of the algorithm, which you can set via `nlopt_set_param(opt, "inner_maxeval", 100)`.
+where the string `name` is the name of an algorithm-specific parameter and `val` is the value you are setting the parameter to. For example, the MMA algorithm has a parameter `"inner_maxeval"`, an upper bound on the number of "inner" iterations of the algorithm, which you can set via `nlopt_set_param(opt, "inner_maxeval", 100)`.
 
 You can also check whether a parameter is set or get the current value of a parameter with
 ```c
-double nlopt_has_param(const nlopt_opt opt, const char *name);
+int nlopt_has_param(const nlopt_opt opt, const char *name);
 double nlopt_get_param(const nlopt_opt opt, const char *name, double defaultval);
 ```
 where `defaultval` is returned by `nlopt_get_param` if the parameter `name` has not been set.