Compile problem with kmix in 3_1_BRANCH

[Pavel Troller]

Hi!
  I was compiling kdemultimedia today and it failed. It seems that somebody
imported some kmix changes from HEAD but forgot to import some png images
to the pics directory (like mix_headphone.png). I've imported them from the
HEAD branch and chattr -i 'd them to prevent them from being erased by
retagging the 3.1 branch. 
                                        With regards, Pavel Troller