Cleanup:Remove C++14 flags from extern/quadriflow

The main CMakeLists.txt specifies C++17, quadriflow tries to add C++14
flags leading to the following warnings when building with MSVC

Command line warning D9025 : overriding '/std:c++17' with '/std:c++14`

This change removes the C++14 flags, and fixes a build error caused
by the removal of `std::unary_function` in C++17 in the .obj loader
(which isn't used by blender)

Reviewed By: zeddb

Differential Revision: https://developer.blender.org/D8720

extern/quadriflow/CMakeLists.txt

@@ -28,9 +28,6 @@ if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_C_COMPILER_ID MATCHES "Clang")
   )
 endif()
 
-set(CMAKE_CXX_STANDARD 14)
-set(CMAKE_CXX_STANDARD_REQUIRED ON)
-
 if(WIN32)
     add_definitions(-D_USE_MATH_DEFINES)
 endif()

extern/quadriflow/patches/blender.patch

@@ -1,3 +1,15 @@
+diff --git a/extern/quadriflow/src/loader.cpp b/extern/quadriflow/src/loader.cpp
+--- a/extern/quadriflow/src/loader.cpp
++++ b/extern/quadriflow/src/loader.cpp
+@@ -69,7 +69,7 @@
+        };
+
+        /// Hash function for obj_vertex
+-       struct obj_vertexHash : std::unary_function<obj_vertex, size_t> {
++       struct obj_vertexHash {
+                std::size_t operator()(const obj_vertex &v) const {
+                        size_t hash = std::hash<uint32_t>()(v.p);
+                        hash = hash * 37 + std::hash<uint32_t>()(v.uv);
 diff --git a/extern/quadriflow/src/config.hpp b/extern/quadriflow/src/config.hpp
 index 842b885..bf597ad 100644
 --- a/extern/quadriflow/src/config.hpp

extern/quadriflow/src/loader.cpp

@@ -69,7 +69,7 @@ void load(const char* filename, MatrixXd& V, MatrixXi& F)
 	};
 
 	/// Hash function for obj_vertex
-	struct obj_vertexHash : std::unary_function<obj_vertex, size_t> {
+	struct obj_vertexHash {
 		std::size_t operator()(const obj_vertex &v) const {
 			size_t hash = std::hash<uint32_t>()(v.p);
 			hash = hash * 37 + std::hash<uint32_t>()(v.uv);