[patch] [kh] PSP podcast support

the problem with PSP is that it want to know the file size by using HEAD request, and will seek to the end of the file by using range request, trying to get the id3 tag. with any step fail, it refuse to play the mp3 (not sure if it handles media beside mp3)

so my patch will

1. add HEAD support
2. add simple range trick. send audio data anyway. because there're many mp3 files without id3 tag, PSP should (and does) accept this case

i took me a lot of time to figure it out as i have no PSP to test. had to bother my friends