app_server: Move DWindowHWInterface and ViewHWInterface to a subdirectory.

AccelerantHWInterface and the Remote engines already did this.
These are not used at all outside of test_app_server, so we do not
need to even compile them in to the regular one.

src/tests/servers/app/Jamfile

@@ -47,6 +47,7 @@ SEARCH_SOURCE += [ FDirName $(appServerDir) decorator ] ;
 SEARCH_SOURCE += [ FDirName $(appServerDir) drawing ] ;
 SEARCH_SOURCE += [ FDirName $(appServerDir) drawing Painter ] ;
 SEARCH_SOURCE += [ FDirName $(appServerDir) drawing interface remote ] ;
+SEARCH_SOURCE += [ FDirName $(appServerDir) drawing interface virtual ] ;
 SEARCH_SOURCE += [ FDirName $(appServerDir) font ] ;
 
 SharedLibrary libhwinterface.so :