Show (short) list of possible enum values when an invalid value is encountered (resolves #1318)

All enum errors have (hopefully) been changed to a luax_enumerror, which has a
fixed error message. If additionally a list of valid options is passed, it
lists that in the error message. For every enum error with few options I've
implemented this using a getConstants call.

This solution has been designed specifically to reduce the number of template
instantiations (as I've been told that was a concern). All new template code
happens in places where there already was an instantiation of the relevant
StringMap. Of course there is still std::vector<std::string>...

--HG--
branch : minor

src/modules/graphics/Mesh.cpp

@@ -659,16 +659,21 @@ size_t Mesh::getAttribFormatSize(const AttribFormat &format)
 	}
 }
 
-bool Mesh::getConstant(const char *in, Mesh::DrawMode &out)
+bool Mesh::getConstant(const char *in, DrawMode &out)
 {
 	return drawModes.find(in, out);
 }
 
-bool Mesh::getConstant(Mesh::DrawMode in, const char *&out)
+bool Mesh::getConstant(DrawMode in, const char *&out)
 {
 	return drawModes.find(in, out);
 }
 
+std::vector<std::string> Mesh::getConstants(DrawMode)
+{
+	return drawModes.getNames();
+}
+
 bool Mesh::getConstant(const char *in, DataType &out)
 {
 	return dataTypes.find(in, out);
@@ -679,6 +684,11 @@ bool Mesh::getConstant(DataType in, const char *&out)
 	return dataTypes.find(in, out);
 }
 
+std::vector<std::string> Mesh::getConstants(DataType)
+{
+	return dataTypes.getNames();
+}
+
 bool Mesh::getConstant(const char *in, AttributeStep &out)
 {
 	return attributeSteps.find(in, out);
@@ -689,6 +699,11 @@ bool Mesh::getConstant(AttributeStep in, const char *&out)
 	return attributeSteps.find(in, out);
 }
 
+std::vector<std::string> Mesh::getConstants(AttributeStep)
+{
+	return attributeSteps.getNames();
+}
+
 StringMap<Mesh::DrawMode, Mesh::DRAWMODE_MAX_ENUM>::Entry Mesh::drawModeEntries[] =
 {
 	{ "fan",       DRAWMODE_FAN       },