[xml] xmlC14NDocDumpMemory inclusive_ns_prefixes parameter not const

[Arnold Hendriks <a hendriks b-lex nl>]

I notice xmlC14NDocDumpMemory (and the related functions) take a 
parameter inclusive_ns_prefixes, but that this parameter is not declared 
as constant.

I wouldn't expect C14N to actually need to change the strings in the 
inclusive_ns_prefixes list, or the list itself. Am I misunderstanding 
the parameter, or was const just ommitted?

With regards,
Arnold Hendriks