(menu_displaylist.c) Some optimizations:
* Make sure val_d is never bigger than 16, it should just
contain a number. 16 is more than plenty (and probably too big even)
* Hose val_d out of loops if its value never changes inside the loop
* Attempt to avoid calling msg_hash_to_str inside loops unnecessarily
as deprecated.
* Use fill_pathname_join_special in the vast majority of cases where
we can ensure out_path is a new empty string
* Get rid of some extension concatenation with strlcat where encountered
* Some general cleanups with NULL termination of strings that get immediately
passed to strlcpy/strlcpy-adjacent functions
* struct was erroneously named 'catagory' - changed to 'category'
* Removed some strlcpys that were just setting the string to a fixed constant value
* Random nits
