manifest: track several external repos we need

aac - merged kk changes into
libxml2 - merged kk changes into it
tinyalsa - merged kk changes into it

icu - prior LP it was handled in icu4c repo which was moved into icu repo. We still need to bring up our changes there
      its pur aosp right now

Change-Id: I9f983b7c8e7c05c79cf5c55845d757fc91451e3c