This function is used to create a new particle system and will
return a unique index number that should be stored and used in all
further functions relating to that system. The system will be
assigned a managed layer and will be set to have a depth of 0.
Managed layers are not accessible to the user and used only for
internal management when depth is used instead of layers. Normally
you would use the function part_system_create_layer
instead of this one.
global.Sname = part_system_create();
This will create a new particle system and store the index in the global variable "Sname".