Ambiguities compiling Phoenix code with _GLIBCXX_DEBUG

[Jeremiah Willcock]

This is a different error than the run-time error in bug #1276. I tried to compile the code in bug #3078 with _GLIBCXX_DEBUG in GCC 4.0.1 and received the following errors (plus many more like this).

boost/spirit/home/phoenix/stl/algorithm/detail/./is_std_map.hpp:38: error: use of 'map' is ambiguous boost/spirit/home/phoenix/stl/algorithm/detail/././std_map_fwd.hpp:30: error: first declared as 'template<class Kty, class Ty, class Pr, class Alloc> struct std::map' here /usr/include/c++/4.0.0/debug/map.h:42: error: also declared as 'template<class _Key, class _Tp, class _Compare, class _Allocator> class gnu_debug_def::map' here

[Steven Watanabe]

(In [53262]) Fix standard container forward declarations. Fixes #3081