Introduce a new library libgvncpulse-1.0.so which provides an
implementation of VncAudio that uses Pulse Audio for output

* Makefile.am, gvncpulse-1.0.pc.in: Add pkgconfig file for
  libgvncpulse
* gtk-vnc.spec.in: Add gvncpulse & gvncpulse-devel sub-RPMS
* src/Makefile.am, src/gvncpulse.h, src/libgvncpulse_sym.version
  Add gvncpulse-1.0 library
* src/vncaudiopulse.c, src/vncaudiopulse.h: Pulse audio
  impl of VncAudio
* vapi/Makefile.am: Build vala binding for pulse audio