Split out Boost.Python
Use boost-python instead of boost => with-python

Boost.Python support in Homebrew is moving from the boost formula to a
new boost-python formula. This commit updates formulas that were using
boost --with-python to use boost-python instead.
boost: update 1.55.0_3 bottle.
boost-python: add 1.55.0 bottle.
ledger: update 3.0.3_1 bottle.
libpst: update 0.6.55_1 bottle.
libtorrent-rasterbar: update 1.0.2_1 bottle.
mapnik: update 2.2.0_3 bottle.
pyexiv2: add 0.3.2_1 bottle.