Fix ruby %alias directive for native c functions

Using the %alias directive on native C functions causes swig to segfault due to
a dereference of klass (which is NULL for native C functions) in the
defineAliases function of the Ruby module. This commit adds support for an alias
of native C functions for both separate module as well as global functions, as
well as three test cases for the %alias directive of the Ruby module.

Fixes:
mod.i
%module ruby_alias
%alias get_my_name "nickname,fullname";
%inline %{
const char *get_my_name(){
  return "Chester Tester";
}
%}
$ swig -ruby mod.i
Segmentation fault

Signed-off-by: Joel Anderson <joelanderson333@gmail.com>

Examples/test-suite/ruby_alias_method.i

@@ -0,0 +1,26 @@
+%module ruby_alias_method
+%include <std_string.i>
+
+%alias Synonym::getMyName "nickname,fullname"
+
+%inline %{
+
+class Synonym {
+private:
+  std::string myName;
+
+public:
+  Synonym(std::string myName);
+
+  std::string getMyName();
+};
+
+Synonym::Synonym(std::string myName){
+  this->myName = myName;
+};
+
+std::string Synonym::getMyName(){
+  return this->myName;
+};
+
+%}