Optional: Move optional-lite to the include/third-party directory

This fixes the use case of adding the include folder
manually to an outside project.

include/icsneo/third-party/optional-lite/example/CMakeLists.txt

@@ -0,0 +1,60 @@
+# Copyright 2017-2018 by Martin Moene
+#
+# https://github.com/martinmoene/optional-lite
+#
+# Distributed under the Boost Software License, Version 1.0.
+# (See accompanying file LICENSE.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+if( NOT DEFINED CMAKE_MINIMUM_REQUIRED_VERSION )
+    cmake_minimum_required( VERSION 3.5 FATAL_ERROR )
+endif()
+
+project( example LANGUAGES CXX )
+
+set( unit_name "optional" )
+set( PACKAGE   ${unit_name}-lite )
+set( PROGRAM   ${unit_name}-lite )
+
+message( STATUS "Subproject '${PROJECT_NAME}', examples '${PROGRAM}-*'")
+
+set( OPTIONS "" )
+
+if( MSVC )
+    message( STATUS "Matched: MSVC")
+
+    set( BASE_OPTIONS -W3 )
+    set( EXCEPTIONS_OPTIONS ${BASE_OPTIONS} -EHsc )
+    set( NO_EXCEPTIONS_OPTIONS ${BASE_OPTIONS} )
+
+elseif( CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang|AppleClang" )
+    message( STATUS "CompilerId: '${CMAKE_CXX_COMPILER_ID}'")
+
+    set( BASE_OPTIONS -Wall -Wextra -Wconversion -Wsign-conversion -Wno-missing-braces -fno-elide-constructors )
+    set( EXCEPTIONS_OPTIONS ${BASE_OPTIONS} )
+    set( NO_EXCEPTIONS_OPTIONS -fno-exceptions )
+
+elseif( CMAKE_CXX_COMPILER_ID MATCHES "Intel" )
+    # as is
+    message( STATUS "Matched: Intel")
+else()
+    # as is
+    message( STATUS "Matched: nothing")
+endif()
+
+function( make_target name no_exceptions )
+    add_executable             ( ${PROGRAM}-${name} ${name}.cpp )
+    target_link_libraries      ( ${PROGRAM}-${name} PRIVATE ${PACKAGE} )
+    if ( no_exceptions )
+        target_compile_options ( ${PROGRAM}-${name} PRIVATE ${NO_EXCEPTIONS_OPTIONS} )
+    else()
+        target_compile_options ( ${PROGRAM}-${name} PRIVATE ${EXCEPTIONS_OPTIONS} )
+    endif()
+
+endfunction()
+
+make_target( 01-to_int FALSE )
+make_target( 02-nodefltctor FALSE )
+# 04-any-optional-variant also requires variant-lite.
+make_target( 05-no-exceptions TRUE )
+
+# end of file