BLI_str_quoted_substrN didn't unescape the resulting string,
yet all callers were using this with animation paths which are
created using BLI_str_escape().
- Fix BLI_str_quoted_substrN use with escaped strings by calling
BLI_str_unescape().
Note that it's possible we want an a version of this function that
keeps escape characters. This could be added if it's required.
- Fix end quote detection using BLI_str_escape_find_quote
checking for `\"` isn't reliable since an even number of back-slashes
before a quote means it's not escaped.
3ec7cf64bc