python: add compatibility with newer versions of swig

Add overloaded methods to avoid ambiguous parameter errors in
newer versions of swig.

Resolves: #114

Author: davvid

src/lib/Partio.h

@@ -290,6 +290,7 @@ ParticlesDataMutable* cloneSchema(const ParticlesData&, const std::map<std::stri
 //! To copy only the detail attributes, pass particles=false.
 //! If attrNameMap is provided, it is used to rename attributes during cloning.
 ParticlesDataMutable* clone(const ParticlesData&, bool particles=true, const std::map<std::string, std::string>* attrNameMap = nullptr);
+ParticlesDataMutable* clone(const ParticlesData&, bool particles, const std::map<std::string, std::string>& attrNameMap);
 
 //! Provides read/write access to a particle set stored in a file
 //! freed with p->release()

src/lib/core/Particle.cpp

@@ -164,6 +164,11 @@ clone(const ParticlesData& other, bool particles, const std::map<std::string, st
     return p;
 }
 
+ParticlesDataMutable*
+clone(const ParticlesData& other, bool particles, const std::map<std::string, std::string>& attrNameMap)
+{
+    return clone(other, particles, &attrNameMap);
+}
 
 template<ParticleAttributeType ETYPE> void
 printAttr(const ParticlesData* p,const ParticleAttribute& attr,const int particleIndex)

src/py/partio.i

@@ -638,7 +638,13 @@ ParticlesDataMutable* cloneSchema(const ParticlesData& other, const std::map<std
 
 %feature("autodoc");
 %feature("docstring","Clone a particle set");
-ParticlesDataMutable* clone(const ParticlesData& other, bool particles, const std::map<std::string, std::string>* attrNameMap=nullptr);
+ParticlesDataMutable* clone(const ParticlesData& other, bool particles, const std::map<std::string, std::string>& attrNameMap);
+
+%pythoncode %{
+def clone(self, particles=True, attrNameMap=None):
+    """Clone a particle set"""
+    return _partio.clone(self, particles, attrNameMap or {})
+%}
 
 %feature("autodoc");
 %feature("docstring","Return string name of given attribute type");