Remove some stuff we don't need:
    third_party libs
    Visual Studio / Xcode files
    symbian files

    pjmedia-audiodev (and update some source files accordingly)
    pjmedia-codec

    tests, documentation

define PJMEDIA_RESAMPLE_IMP PJMEDIA_RESAMPLE_NONE
    => so we don't rely on resample library

define PJMEDIA_HAS_SRTP     0
    => so we don't rely on srtp library

We do resampling and srtp ourselves anyway