Remove arch target from default flags

it messes up with -DUSE_BOOST_SIMD
Support array indexing through an array for any numpy expression
Fix several memory leaks

When initializing an ndarray from a pointer, do not automatically set
the memory as foreign. Do it only if asked too, i.e. if the memory comes
from Python.
Merge pull request #186 from serge-sans-paille/filter

Filter