Use conforming is_class for EDG compilers

Make is_enum work for class types which are convertible to anything at
all (on many compilers).

smart_ptr library workarounds for __MWERKS__ (must use member function
pointer for unspecified_bool_type).


[SVN r20244]

libs/smart_ptr

@@ -1 +1 @@
-Subproject commit 26a93f224e23cd76b8108f20086e6f4eb12546fb
+Subproject commit feff6e40ea4de1013e3e11fda95e3eb0f04322b9

libs/type_traits

@@ -1 +1 @@
-Subproject commit 9c7099c69362c7c5ea18b42602901b4fd469f60d
+Subproject commit 416038f37daf255917103957f2aaab6fe670fd49