fix getkey_string test to use the correct mode
regen
Fix getkey_string expected results
Rework lki_format_keys() to return result on stack.

Use luaL_Buffer in lki_format_keys() to allow arbitrary path lengths.
Add iMaxKeys argument to lki_set_error_keys() and pass to lki_format_keys().
Pass full key path when using getkeys variation.

When getkeys_*() calls a function, pass in the formatted keys argument as
	"key1"."key2"."key3"
instead of just the final component as
	key3