Use extern for *_rtcd() in test/test_libvpx.cc
Use extern for *_rtcd() in test/test_libvpx.cc

This partially reverts commit 14ef4aeafb

Including the rtcd headers to get the function definitions causes
problems on VS9.

Change-Id: I780874d9e03af2d3124192ab0e3907301f22674c

running770/libvpx,shacklettbp/aom,GrokImageCompression/aom,thdav/aom,Topopiccione/libvpx,goodleixiao/vpx,luctrudeau/aom,mbebenita/aom,mwgoldsmith/vpx,shacklettbp/aom,webmproject/libvpx,kalli123/webm.libvpx,webmproject/libvpx,stewnorriss/libvpx,abwiz0086/webm.libvpx,zofuthan/libvpx,thdav/aom,jacklicn/webm.libvpx,felipebetancur/libvpx,zofuthan/libvpx,jmvalin/aom,stewnorriss/libvpx,goodleixiao/vpx,mbebenita/aom,liqianggao/libvpx,running770/libvpx,shyamalschandra/libvpx,Suvarna1488/webm.libvpx,smarter/aom,lyx2014/libvpx_c,mbebenita/aom,VTCSecureLLC/libvpx,shyamalschandra/libvpx,mwgoldsmith/libvpx,lyx2014/libvpx_c,Suvarna1488/webm.libvpx,abwiz0086/webm.libvpx,Topopiccione/libvpx,GrokImageCompression/aom,kalli123/webm.libvpx,thdav/aom,lyx2014/libvpx_c,smarter/aom,mwgoldsmith/vpx,shacklettbp/aom,shacklettbp/aom,kalli123/webm.libvpx,Suvarna1488/webm.libvpx,liqianggao/libvpx,webmproject/libvpx,jacklicn/webm.libvpx,openpeer/libvpx_new,mwgoldsmith/libvpx,openpeer/libvpx_new,goodleixiao/vpx,smarter/aom,goodleixiao/vpx,ittiamvpx/libvpx-1,jmvalin/aom,goodleixiao/vpx,luctrudeau/aom,mbebenita/aom,ShiftMediaProject/libvpx,felipebetancur/libvpx,ittiamvpx/libvpx-1,GrokImageCompression/aom,abwiz0086/webm.libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,jacklicn/webm.libvpx,zofuthan/libvpx,felipebetancur/libvpx,mwgoldsmith/libvpx,shacklettbp/aom,mbebenita/aom,webmproject/libvpx,shyamalschandra/libvpx,ittiamvpx/libvpx-1,Suvarna1488/webm.libvpx,stewnorriss/libvpx,mwgoldsmith/libvpx,jacklicn/webm.libvpx,mbebenita/aom,abwiz0086/webm.libvpx,VTCSecureLLC/libvpx,liqianggao/libvpx,jacklicn/webm.libvpx,liqianggao/libvpx,liqianggao/libvpx,luctrudeau/aom,mwgoldsmith/vpx,VTCSecureLLC/libvpx,lyx2014/libvpx_c,smarter/aom,zofuthan/libvpx,felipebetancur/libvpx,abwiz0086/webm.libvpx,felipebetancur/libvpx,jacklicn/webm.libvpx,openpeer/libvpx_new,shyamalschandra/libvpx,openpeer/libvpx_new,thdav/aom,VTCSecureLLC/libvpx,running770/libvpx,mwgoldsmith/vpx,running770/libvpx,smarter/aom,Suvarna1488/webm.libvpx,gshORTON/webm.libvpx,mbebenita/aom,liqianggao/libvpx,gshORTON/webm.libvpx,felipebetancur/libvpx,openpeer/libvpx_new,kalli123/webm.libvpx,ittiamvpx/libvpx-1,Topopiccione/libvpx,running770/libvpx,mbebenita/aom,ittiamvpx/libvpx-1,mwgoldsmith/vpx,thdav/aom,jmvalin/aom,abwiz0086/webm.libvpx,Topopiccione/libvpx,stewnorriss/libvpx,mwgoldsmith/vpx,GrokImageCompression/aom,Suvarna1488/webm.libvpx,stewnorriss/libvpx,GrokImageCompression/aom,lyx2014/libvpx_c,luctrudeau/aom,jmvalin/aom,ittiamvpx/libvpx-1,zofuthan/libvpx,openpeer/libvpx_new,lyx2014/libvpx_c,running770/libvpx,luctrudeau/aom,thdav/aom,kalli123/webm.libvpx,GrokImageCompression/aom,ShiftMediaProject/libvpx,shyamalschandra/libvpx,jmvalin/aom,webmproject/libvpx,VTCSecureLLC/libvpx,kalli123/webm.libvpx,Topopiccione/libvpx,luctrudeau/aom,jmvalin/aom,shyamalschandra/libvpx,stewnorriss/libvpx,smarter/aom,gshORTON/webm.libvpx,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,zofuthan/libvpx,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,gshORTON/webm.libvpx,Topopiccione/libvpx,mbebenita/aom,shacklettbp/aom,gshORTON/webm.libvpx,goodleixiao/vpx,gshORTON/webm.libvpx,VTCSecureLLC/libvpx