I've made a seperate version (c_index() etc) that use const/const, but
I'm not sure it's worth it considering there is one file in the tree
that uses index on const strings (kern_linker.c) and it's easily adjusted
to scan the strings directly (and is perhaps more efficient that way).
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.