abcde: Relax filename munging for Linux filesystems

In the interest of not messing with colons in filenames (among other
characters), this function has been changed to only remove control
characters and convert '/' to '-'. In the future, this should be updated
to check the current filesystem and use the appropriate munging for it.

Ref: https://stackoverflow.com/a/35352640/540162

src/.abcde.conf

@@ -29,11 +29,12 @@ VAONETRACKOUTPUTFORMAT='${OUTPUT}/Other, Various Artists/${ARTISTFILE} - ${TRACK
 # mungefilename receives the CDDB data (artist, track, title, whatever) as $1
 # and outputs it on stdout.
 # This custom function will do the following:
-#  * Eat printable ASCII characters which are forbidden in Windows and Linux
+#  * Eat control characters
-#    (<>:"/\|?*) and control characters
+#  * Convert '/' to '-' to ensure valid filenames on ext2/ext3/ext4 filesystems
+# TODO: add checks for other filesystems (FAT32, NFTS for Windows, HFS, HFS+ for MacOS)
 mungefilename ()
 {
-  echo "$@" | tr -d "<>:\"/\\\\|?*[:cntrl:]"
+  echo "$@" | tr -d '[:cntrl:]' | tr '/' '-'
 }
 
 # Embed album art in addition to default actions