ledger fails to build against boost 1.59.0

[Tim Smith]

Ledger 3.1 fails to build on OS X against Boost 1.59.0.

A transcript of the build is here: https://gist.github.com/anonymous/258c90fcde8c801287ae#file-01-acprep-L139

The failures look like:

[ 70%] Building CXX object src/CMakeFiles/libledger.dir/py_commodity.cc.o

/tmp/ledger20150814-16604-u40p80/ledger-3.1/src/py_amount.cc:131:26: error: no matching function for call to 'make_setter'

                         make_setter(&amount_t::is_initialized))

                         ^~~~~~~~~~~

Homebrew is tracking packages which fail to build against Boost 1.59.0 at https://github.com/Homebrew/homebrew/pull/42960.

Thanks,

Tim Smith