Fix FTBFS with Boost 1.49.0

The implementation of BOOST_PP_ITERATION_FLAGS() changed in Boost 1.49.0,
which causes Luabind to fail to build with GCC (reproduced with GCC 4.4
and GCC 4.6).

https://svn.boost.org/trac/boost/ticket/6631

http://thread.gmane.org/gmane.comp.lib.boost.devel/228802

http://article.gmane.org/gmane.comp.lib.boost.devel/228836

The work-around is to replace the pattern

 #if !defined(MACRO)
     // A
 #elif MACRO()
     // B
 #endif

with

 #if !defined(MACRO)
     // A
 #else
     #if MACRO()
         // B
     #endif
 #endif

luabind/detail/call_function.hpp

@@ -323,7 +323,8 @@ namespace luabind
 
 #endif // LUABIND_CALL_FUNCTION_HPP_INCLUDED
 
-#elif BOOST_PP_ITERATION_FLAGS() == 1
+#else
+#if BOOST_PP_ITERATION_FLAGS() == 1
 
 #define LUABIND_TUPLE_PARAMS(z, n, data) const A##n *
 #define LUABIND_OPERATOR_PARAMS(z, n, data) const A##n & a##n
@@ -438,4 +439,5 @@ namespace luabind
 
 
 #endif
+#endif
 

luabind/detail/call_member.hpp

@@ -316,7 +316,8 @@ namespace luabind
 
 #endif // LUABIND_CALL_MEMBER_HPP_INCLUDED
 
-#elif BOOST_PP_ITERATION_FLAGS() == 1
+#else
+#if BOOST_PP_ITERATION_FLAGS() == 1
 
 #define LUABIND_TUPLE_PARAMS(z, n, data) const A##n *
 #define LUABIND_OPERATOR_PARAMS(z, n, data) const A##n & a##n
@@ -360,4 +361,5 @@ namespace luabind
 #undef LUABIND_TUPLE_PARAMS
 
 #endif
+#endif
 

luabind/wrapper_base.hpp

@@ -89,7 +89,8 @@ namespace luabind
 
 #endif // LUABIND_WRAPPER_BASE_HPP_INCLUDED
 
-#elif BOOST_PP_ITERATION_FLAGS() == 1
+#else
+#if BOOST_PP_ITERATION_FLAGS() == 1
 
 #define LUABIND_TUPLE_PARAMS(z, n, data) const A##n *
 #define LUABIND_OPERATOR_PARAMS(z, n, data) const A##n & a##n
@@ -188,3 +189,4 @@ namespace luabind
 #undef N
 
 #endif
+#endif