Merge pull request #15869 from TolyaTalamanov:at/plaidml-backend

G-API: Implement PlaidML2 backend

* PlaidML backend init version

* Add test

* Support multiply inputs/outputs in PlaidML2 backend

* Fix comment to review

* Add HAVE_PLAIDML macros

* Move plaidml tests to separate file

* Fix comment to review

* Fix cmake warning

* Fix comments to review

* Fix typos

overload -> overflow

* Fix comments to review

* Clean up

* Remove spaces from cmake scripts
* Disable tests with bitwise operations

* Use plaidml::exec::Binder

modules/gapi/cmake/init.cmake

@@ -1,10 +1,11 @@
 OCV_OPTION(WITH_ADE "Enable ADE framework (required for Graph API module)" ON)
+OCV_OPTION(WITH_PLAIDML "Include PlaidML2 support" OFF)
 
 if(NOT WITH_ADE)
   return()
 endif()
 
-if (ade_DIR)
+if(ade_DIR)
   # if ade_DIR is set, use ADE-supplied CMake script
   # to set up variables to the prebuilt ADE
   find_package(ade 0.1.0)
@@ -15,3 +16,10 @@ if(NOT TARGET ade)
   # downloaded one (if there any)
   include("${CMAKE_CURRENT_LIST_DIR}/DownloadADE.cmake")
 endif()
+
+if(WITH_PLAIDML)
+  find_package(PlaidML2 CONFIG QUIET)
+  if (PLAIDML_FOUND)
+      set(HAVE_PLAIDML TRUE)
+  endif()
+endif()