vpxdec: make some functions static
vpxdec: make some functions static

silences missing-prototype warnings

Change-Id: I080d2a24eeb6faa8c160683cc1fbf30d3b0b49e5

liqianggao/libvpx,mwgoldsmith/libvpx,shacklettbp/aom,felipebetancur/libvpx,mbebenita/aom,shacklettbp/aom,ittiamvpx/libvpx-1,Topopiccione/libvpx,goodleixiao/vpx,liqianggao/libvpx,luctrudeau/aom,jmvalin/aom,liqianggao/libvpx,jmvalin/aom,VTCSecureLLC/libvpx,openpeer/libvpx_new,webmproject/libvpx,zofuthan/libvpx,smarter/aom,ittiamvpx/libvpx-1,ShiftMediaProject/libvpx,running770/libvpx,shyamalschandra/libvpx,mbebenita/aom,smarter/aom,felipebetancur/libvpx,ittiamvpx/libvpx-1,mwgoldsmith/libvpx,mwgoldsmith/vpx,ittiamvpx/libvpx-1,thdav/aom,webmproject/libvpx,jmvalin/aom,felipebetancur/libvpx,shyamalschandra/libvpx,ittiamvpx/libvpx-1,ShiftMediaProject/libvpx,shacklettbp/aom,stewnorriss/libvpx,luctrudeau/aom,GrokImageCompression/aom,mwgoldsmith/vpx,zofuthan/libvpx,mwgoldsmith/libvpx,webmproject/libvpx,running770/libvpx,ittiamvpx/libvpx-1,smarter/aom,GrokImageCompression/aom,Topopiccione/libvpx,openpeer/libvpx_new,Topopiccione/libvpx,stewnorriss/libvpx,webmproject/libvpx,mbebenita/aom,stewnorriss/libvpx,ShiftMediaProject/libvpx,openpeer/libvpx_new,mwgoldsmith/vpx,luctrudeau/aom,shyamalschandra/libvpx,running770/libvpx,GrokImageCompression/aom,mbebenita/aom,liqianggao/libvpx,luctrudeau/aom,goodleixiao/vpx,shyamalschandra/libvpx,stewnorriss/libvpx,zofuthan/libvpx,thdav/aom,webmproject/libvpx,shyamalschandra/libvpx,openpeer/libvpx_new,mbebenita/aom,luctrudeau/aom,VTCSecureLLC/libvpx,GrokImageCompression/aom,liqianggao/libvpx,mwgoldsmith/libvpx,zofuthan/libvpx,running770/libvpx,smarter/aom,goodleixiao/vpx,Topopiccione/libvpx,thdav/aom,luctrudeau/aom,goodleixiao/vpx,jmvalin/aom,thdav/aom,Topopiccione/libvpx,VTCSecureLLC/libvpx,jmvalin/aom,felipebetancur/libvpx,VTCSecureLLC/libvpx,shyamalschandra/libvpx,running770/libvpx,liqianggao/libvpx,mwgoldsmith/libvpx,mbebenita/aom,shacklettbp/aom,shacklettbp/aom,openpeer/libvpx_new,GrokImageCompression/aom,thdav/aom,jmvalin/aom,shacklettbp/aom,mbebenita/aom,zofuthan/libvpx,GrokImageCompression/aom,felipebetancur/libvpx,smarter/aom,VTCSecureLLC/libvpx,smarter/aom,mbebenita/aom,thdav/aom,mwgoldsmith/vpx,stewnorriss/libvpx,zofuthan/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,mbebenita/aom,goodleixiao/vpx,Topopiccione/libvpx,running770/libvpx,VTCSecureLLC/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,felipebetancur/libvpx,stewnorriss/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx,openpeer/libvpx_new,goodleixiao/vpx