[lmi] "error: forward declaration of `st,ruct wxDataFormat'"

[Greg Chicares]

With wx-2.9, MinGW gcc-3.4.5, and libstdc++ debug mode, the compiler
complains about forward-declaring wxDataObject in 'wx/clipbrd.h'.
This occurs in an lmi file which includes these headers:
  #include <wx/clipbrd.h>
  #include <wx/dataobj.h>
in that order. The diagnostic "goes away" if I swap the inclusion
order, so I'm not seriously inconvenienced. I suppose it's due to
'-D_GLIBCXX_CONCEPT_CHECKS' testing whether the wxVector elements
are Assignable:

  line in 'wx/clipbrd.h'
    24 class WXDLLIMPEXP_FWD_CORE wxDataFormat;
   117     wxVector<wxDataFormat> m_formats;

I guess it wouldn't be helpful to unwrap lines this long:

/MinGW_/bin/g++  -MMD -MP -MT wx_utility.o -MF wx_utility.d  -c -I /lmi/src/lmi
-I /lmi/src/lmi/tools/pete-2.1.1 -I /opt/lmi/local/lib/wx/include/i686-pc-mingw3
2-msw-unicode-release-2.9 -I /opt/lmi/local/include/wx-2.9 -I /opt/lmi/third_par
ty/include -I /opt/lmi/third_party/src -I /opt/lmi/local/include -I /opt/lmi/loc
al/include/libxml2 -DLMI_WX_NEW_USE_SO  -DLIBXML_USE_DLL -DSTRICT  -D_GLIBCXX_DE
BUG -D_GLIBCXX_DEBUG_PEDANTIC -D_GLIBCXX_CONCEPT_CHECKS -D_GLIBCPP_DEBUG -D_GLIB
CPP_DEBUG_PEDANTIC -D_GLIBCPP_CONCEPT_CHECKS -D_GLIBXX_DEBUG_PEDANTIC   -D_LARGE
FILE_SOURCE=unknown -DWXUSINGDLL -D__WXMSW__ -DBOOST_STRICT_CONFIG   -std=gnu++9
8 -posix -pedantic-errors -Werror -Wall -Wcast-align -Wconversion -Wdeprecated-d
eclarations -Wdisabled-optimization -Wimport -Wmultichar -Wpacked -Wpointer-arit
h -Wsign-compare -Wundef -Wwrite-strings  -Wno-long-long -Wctor-dtor-privacy -Wd
eprecated -Wnon-template-friend -Woverloaded-virtual -Wpmf-conversions -Wsynth
 -Wno-uninitialized    -ggdb -O0   /lmi/src/lmi/wx_utility.cpp -owx_utility.o
In file included from /lmi/src/lmi/wx_utility.cpp:39:
C:/opt/lmi/MinGW-20090203/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3
.4.5/bits/boost_concept_check.h: In instantiation of `__gnu_cxx::_SGIAssignableC
oncept<wxDataFormat>':
C:/opt/lmi/MinGW-20090203/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3
.4.5/bits/stl_vector.h:144:   instantiated from `__gnu_norm::vector<wxDataFormat
, std::allocator<wxDataFormat> >'
C:/opt/lmi/MinGW-20090203/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3
.4.5/debug/vector:46:   instantiated from `__gnu_debug_def::vector<wxDataFormat,
 std::allocator<wxDataFormat> >'
/opt/lmi/local/include/wx-2.9/wx/clipbrd.h:117:   instantiated from here
C:/opt/lmi/MinGW-20090203/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3
.4.5/bits/boost_concept_check.h:216: error: `__gnu_cxx::_SGIAssignableConcept<_T
p>::__a' has incomplete type
/opt/lmi/local/include/wx-2.9/wx/clipbrd.h:24: error: forward declaration of `st
ruct wxDataFormat'