Modernize the code base to C++11 standards and beyond.

Apply `clang-modernize` (based on Clang 3.6) transformations to the
codebase while making sure to support Clang>=3.4 and GCC>=4.8.

We apply the transformations in parallel to speed up the quite
time consuming process, and use our `clang-format` style file
to automatically format the code respecting our coding conventions.

We use the following self-explanatory transformations:

* AddOverride
* LoopConvert
* PassByValue
* ReplaceAutoPtr
* UseAuto
* UseNullptr

This required a `compile_commands.json` compilation database, e.g.

    ccmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_EXPORT_COMPILE_COMMANDS=1

for CMake or check Bear for a Makefile based solution (or even Ninja).

    git ls-files -x '*.cpp|*.h' | \
      xargs -I{} -P $(nproc) clang-modernize -p build -final-syntax-check -format -style=file -summary -for-compilers=clang-3.4,gcc-4.8 -include . -exclude third_party {}

Boom!

References:

* http://clang.llvm.org/extra/clang-modernize.html
* http://clang.llvm.org/extra/ModernizerUsage.html

data_structures/static_rtree.hpp

@@ -316,8 +316,8 @@ class StaticRTree
     using IncrementalQueryNodeType = mapbox::util::variant<TreeNode, EdgeDataT>;
     struct IncrementalQueryCandidate
     {
-        explicit IncrementalQueryCandidate(const float dist, const IncrementalQueryNodeType &node)
-            : min_dist(dist), node(node)
+        explicit IncrementalQueryCandidate(const float dist, IncrementalQueryNodeType node)
+            : min_dist(dist), node(std::move(node))
         {
         }
 
@@ -553,7 +553,7 @@ class StaticRTree
                          const boost::filesystem::path &leaf_file,
                          std::shared_ptr<CoordinateListT> coordinate_list)
         : m_search_tree(tree_node_ptr, number_of_nodes), m_leaf_node_filename(leaf_file.string()),
-          m_coordinate_list(coordinate_list)
+          m_coordinate_list(std::move(coordinate_list))
     {
         // open leaf node file and store thread specific pointer
         if (!boost::filesystem::exists(leaf_file))