Add minimal test for UBSan failures

Reproduced with clang 5.0 and 6.0 on Linux using Boost super-project at
master as well as Function at develop:

cd libs/function/test/ubsan_undefined_bug
b2 toolset=clang variant=ubsan_undefined

test/ubsan_undefined_bug/Jamfile

@@ -0,0 +1,18 @@
+import testing ;
+
+variant ubsan_undefined
+    : release
+    :
+    <cxxflags>"-std=c++11 -Wno-unused -fstrict-aliasing -fno-omit-frame-pointer -fsanitize=undefined -fno-sanitize-recover=undefined"
+    <linkflags>"-fsanitize=undefined"
+    <debug-symbols>on
+    <define>BOOST_USE_ASAN=1
+    ;
+
+project
+    : requirements
+    <include>$(BOOST_ROOT)
+    <library>/boost/test//boost_unit_test_framework
+    ;
+
+run test.cpp ;

test/ubsan_undefined_bug/test.cpp

@@ -0,0 +1,11 @@
+#define BOOST_TEST_MAIN
+#include <boost/test/unit_test.hpp>
+
+BOOST_AUTO_TEST_SUITE( ubsan_tests )
+
+BOOST_AUTO_TEST_CASE( test1 )
+{
+    BOOST_CHECK(true);
+}
+
+BOOST_AUTO_TEST_SUITE_END()