cppdom: fix compile failure

``brew install cppdom`` failed with messages:

~~~text
In file included from cppdom/cppdom.cpp:51:
/usr/local/include/cppdom-1.2.0/cppdom/cppdom.h:82:18: fatal error: 'tr1/unordered_map' file not found
#        include <tr1/unordered_map>
                 ^
1 error generated.
~~~

and,

~~~text
/usr/local/include/cppdom-1.2.0/cppdom/SpiritParser.h:51:10: fatal error: 'boost/spirit/core.hpp' file not found
#include <boost/spirit/core.hpp>
         ^
1 error generated.
scons: *** [build.darwin/type-optimized--arch-x64/cppdom/SpiritParser.o] Error 1
scons: building terminated because of errors.
~~~

These issues have been already reported to upstream:

* https://sourceforge.net/p/xml-cppdom/patches/5/
* https://sourceforge.net/p/xml-cppdom/patches/6/
Can you link to the upstream bug reports as comments in the formulae? Thanks!