Merge pull request #2606 from alalek:icv_downloader

cmake/OpenCVFindIPP.cmake

@@ -140,7 +140,7 @@ macro(ipp_detect_version)
     else()
       _ipp_not_supported("IPP ${IPP_VERSION_STR} at ${IPP_ROOT_DIR} is not supported")
     endif()
-    if(X86_64)
+    if(IPP_X64)
       _ipp_set_library_dir(${IPP_LIBRARY_DIR}/intel64)
     else()
       _ipp_set_library_dir(${IPP_LIBRARY_DIR}/ia32)
@@ -221,7 +221,12 @@ if(DEFINED ENV{OPENCV_IPP_PATH} AND NOT DEFINED IPPROOT)
   set(IPPROOT "$ENV{OPENCV_IPP_PATH}")
 endif()
 if(NOT DEFINED IPPROOT)
-  set(IPPROOT "${OpenCV_SOURCE_DIR}/3rdparty/ippicv")
+  include("${OpenCV_SOURCE_DIR}/3rdparty/ippicv/downloader.cmake")
+  if(DEFINED OPENCV_ICV_PATH)
+    set(IPPROOT "${OPENCV_ICV_PATH}")
+  else()
+    return()
+  endif()
 endif()
 
 # Try ICV