python plugin: Try to avoid casting errors with Sun's cc.

python plugin: Try to avoid casting errors with Sun's cc.

"python.c", line 534: warning: argument #1 is incompatible with prototype:
	prototype: pointer to void : "python.c", line 470
	argument : pointer to function(pointer to const char, pointer to function(..) returning void, pointer to struct user_data_s {pointer to void data, pointer to function(..) returning void free_func}) returning int
"python.c", line 534: warning: argument #2 is incompatible with prototype:
	prototype: pointer to void : "python.c", line 470
	argument : pointer to function(int, pointer to const char, pointer to struct user_data_s {pointer to void data, pointer to function(..) returning void free_func}) returning void