libraries/id3lib: apply Debian patches

Apply all patches maintained by Debian team. Upstream hasn't been developed since 2003, and the SlackBuild hasn't been updated for a decade. Apart from the corrections of UTF-related bugs, these patches contain important security fixes for stack smashing and null-pointer dereference. Pat is applying some of these patches in -current as well.

Clean up SlackBuild script. Align with template where possible, remove unnecessary additions. Don't build the API documentation - it was built only to be removed before package creation. Reduce the amount of installed documentation, install the same docs as -current does. One of the patches provides man pages for utilities distributed with the library. They are installed in the same way as in -current.