[lmi] Upgrading to gcc-4.9.2

[Greg Chicares]

gcc-3.4.5 was released 2005-11-30, just over ten years ago. It's high
time we upgraded. It's also time to forsake the moribund mingw.org and
migrate to MinGW-w64, which is the standard cross compiler in all
GNU/Linux distributions. (I'm running debian GNU/Linux, and I've been
building lmi in an msw VM, using Cygwin to emulate a POSIX environment,
and that's just silly.) Initially, at least, we'll keep building 32-bit
binaries; later, we can consider building 64-bit binaries.

This is such a big step forward that I'm reluctant to change anything
else at the same time. The decade-old version of 'boost' that we're
using suffers from this problem:
  http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_412.htm
but this workaround:
  https://svn.boost.org/trac/boost/ticket/2069#comment:2
seems good enough for now.

I'm surprised if this hasn't been noticed:

In file included from /opt/lmi/local/include/wx/pdfdocument.h:25:0,
                 from /opt/lmi/local/include/wx/pdfdc.h:21,
                 from /lmi/src/lmi/group_quote_pdf_gen_wx.cpp:56:
/opt/lmi/local/include/wx/pdfarraytypes.h:27:86: error: invoking macro 
WX_DEFINE_SORTED_USER_EXPORTED_TYPEARRAY argument 4: empty macro arguments are 
undefined in ISO C90 and ISO C++98
 WX_DEFINE_SORTED_USER_EXPORTED_ARRAY_INT(int, wxPdfSortedArrayInt, 
WXDLLIMPEXP_PDFDOC);
                                                                                
      ^
but I imagine that's easy to fix if you know how. Vadim, could you
please look into that? A local patch would be fine. That's the only
compiler error remaining in my local tree, and I'd like to find out
whether our binaries link.