Update gtl::Hash so that std::hash<Foo*> can be overridden

Author: greg7mdp

docs/new_release.md

@@ -0,0 +1,40 @@
+- update version in gtl_config.hpp
+- update version in comment on top of CMakeLists.txt and in README.md
+- git commit
+- git push
+- create the new release on github (tag `v1.1.5` - use semantic versioning)
+- download the tar.gz from github, and use `sha256sum gtl-1.1.5.tar.gz` on linux to get the sha256
+
+## conan
+
+- fork and clone [conan-center repo](https://github.com/conan-io/conan-center-index)
+     (or sync +  git pull)
+- git checkout -b gtl_1.1.5
+- update: `recipes/gtl/all/conandata.yml` and `recipes/gtl/config.yml`
+- sudo pip install conan -U 
+- cd recipes/gtl/all
+- conan create conanfile.py gtl/1.1.5@ -pr:b=default -pr:h=default 
+- git diff
+- git commit ...
+- git push origin gtl_1.1.5 
+- create PR like [this](https://github.com/conan-io/conan-center-index/pull/13161)
+
+
+## vcpkg
+
+- fork and clone [vcpkg repo](https://github.com/microsoft/vcpkg)
+     (or sync +  git pull)
+- git checkout -b gtl_1.1.5
+- update ports/gtl/portfile.cmake and ports/gtl/vcpkg.json
+
+in windows, non-cygwin console
+
+- set VCPKG_ROOT=
+- vcpkg install gtl --triplet x64-windows
+- # update sha in portfile.cmake
+- git diff
+- git commit ...
+- vcpkg x-add-version --all --overwrite-version ## (or ./vcpkg.exe --no-dry-run upgrade )
+- git diff
+- git commit ...
+- git push origin gtl_1.1.5 

include/gtl/phmap.hpp

@@ -4932,7 +4932,9 @@ struct HashEq<T*>
         using is_transparent = void;
         template <class U>
         size_t operator()(const U& ptr) const {
-            return gtl::Hash<const T*>{}(HashEq::ToPtr(ptr));
+            // we want phmap::Hash<T*> and not phmap::Hash<const T*>
+            // so "struct std::hash<T*> " override works
+            return gtl::Hash<T*>{}((T*)(uintptr_t)HashEq::ToPtr(ptr));
         }
     };
 

include/gtl/phmap_utils.hpp

@@ -166,15 +166,6 @@ struct Hash
     }
 };
 
-template <class T>
-struct Hash<T *>
-{
-    inline size_t operator()(const T *val) const noexcept
-    {
-        return static_cast<size_t>(reinterpret_cast<const uintptr_t>(val)); 
-    }
-};
-
 template<class ArgumentType, class ResultType>
 struct gtl_unary_function
 {