autoresume: Match full directory path names only in autoresumable()

autoresume: Match full directory path names only in autoresumable()

Removed genre-tag matching (considered too fragile for real-world use).

Removed substring matching for file names.  To avoid unintended
matches, the search pattern now must match the file's full dir name
(or a parent directory thereof), anchored in the root directory.

Search strings now must be delimited with ":" rather than ",".  The
default list of directories is "/podcast:/podcasts" (case-insensitive).

Made implementation somewhat more efficient (don't use strtok -> no
need to copy the string to private storage (stack) before tokenizing
it).

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29280 a1c6a512-1295-4272-9138-f99709370657