- Remove dependency of vlc on stamp-builtin with shared libvlc

- Link against -lvlc instead of src/libvlc.so otherwise installed vlc
  cannot be loaded (closes #555)
- Remove src/libvlc.a when src/libvlc.so is built so that previous item
  does not break Win32 linking

<subliminal message>how about using libtool</subliminal message>