Don't check for live555 headers twice

If the version header is there, the main one should be too.

configure.ac

@@ -1765,7 +1765,6 @@ lternatively you can use --disable-live555 to disable the liveMedia plugin.])
 
           dnl We need to check for pic because live555 don't provide shared libs
           dnl and we want to build a plugins so we need -fPIC on some arch.
-          AC_CHECK_HEADERS(liveMedia.hh, [
           VLC_ADD_CXXFLAGS([live555], [${CPPFLAGS_live555}])
           AC_CHECK_LIB(liveMedia_pic, main, [
             VLC_ADD_PLUGIN([live555])
@@ -1775,9 +1774,6 @@ lternatively you can use --disable-live555 to disable the liveMedia plugin.])
             VLC_ADD_PLUGIN([live555])
             VLC_ADD_LIBS([live555], [-lliveMedia ${other_libs}])
           ],[],[${other_libs}]) ],[${other_libs_pic}])
-          ],[
-           AC_MSG_WARN([The development files for liveMedia (live555) can't be found])
-          ])
 
           CPPFLAGS="${CPPFLAGS_save}"
           AC_LANG_POP(C++)