build: switch to C++14

Replace our homegrown implementation of optional (based
on Boost.Optional) with optional-lite by Martin Moene.

Change-Id: I4632cbc7c705a94af0b85a335515e3430bf3cb1f
Refs: #3076
diff --git a/docs/doxygen.conf.in b/docs/doxygen.conf.in
index d3d4c5a..30dd69b 100644
--- a/docs/doxygen.conf.in
+++ b/docs/doxygen.conf.in
@@ -2050,13 +2050,18 @@
 # This tag requires that the tag ENABLE_PREPROCESSING is set to YES.
 
 PREDEFINED             = DOXYGEN \
+                         BOOST_CONCEPT_ASSERT(x)= \
+                         BOOST_CONCEPT_REQUIRES(x)= \
                          NDN_CXX_DECLARE_WIRE_ENCODE_INSTANTIATIONS(x)= \
                          NDN_LOG_INIT(x)= \
+                         NDN_LOG_MEMBER_DECL()= \
+                         NDN_LOG_MEMBER_DECL_SPECIALIZED(x)= \
+                         NDN_LOG_MEMBER_INIT(x,y)= \
+                         NDN_LOG_MEMBER_INIT_SPECIALIZED(x,y)= \
                          PUBLIC_WITH_TESTS_ELSE_PROTECTED=protected \
                          PUBLIC_WITH_TESTS_ELSE_PRIVATE=private \
                          PROTECTED_WITH_TESTS_ELSE_PRIVATE=private \
-                         VIRTUAL_WITH_TESTS= \
-                         BOOST_CONCEPT_ASSERT(x)=
+                         VIRTUAL_WITH_TESTS=
 
 # If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then this
 # tag can be used to specify a list of macro names that should be expanded. The