Make nested boost::assign::map_list_of work in C++11 mode

Adding a layer of indirection here seems necessary to avoid ambiguities
introduced by new C++11 features.  The extra layer forces a call to the
implicit conversion operator defined for converting the boost
initialization list format to std::map.
Merge pull request #14 from c42f/assign-cxx11-fix

Make nested boost::assign::map_list_of work in C++11 mode
Fixed issue #15
Fix broken install when doxygen is not found
Merge pull request #16 from c42f/no-doc-build-fix

Fix broken install when doxygen is not found
In-place filters and testsuite for them