cmake: Bump required C++ standard version to C++17

Note this adds a boost-specific #define to avoid using
deprecated STL features that have been removed on some
platforms. See #2634.

Fixes #2634

(Internal change: 2295937)

cmake/defaults/CXXDefaults.cmake

@@ -25,8 +25,8 @@ include(CXXHelpers)
 include(Version)
 include(Options)
 
-# Require C++14
-set(CMAKE_CXX_STANDARD 14)
+# Require C++17
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
@@ -44,6 +44,11 @@ _add_define(GLX_GLXEXT_PROTOTYPES)
 # Python bindings for tf require this define.
 _add_define(BOOST_PYTHON_NO_PY_SIGNATURES)
 
+# Parts of boost (in particular, boost::hash) rely on deprecated features
+# of the STL that have been removed from some implementations under C++17.
+# This define tells boost not to use those features.
+_add_define(BOOST_NO_CXX98_FUNCTION_BASE)
+
 if(CMAKE_BUILD_TYPE STREQUAL "Debug")
     _add_define(BUILD_OPTLEVEL_DEV)
 endif()