Implement PEP 465: dedicated infix operator for matrix multiplication

treat unknown (builtin) names as potential globals instead of requiring them to be builtins at runtime

DOC: Updates EPD references to refer to Canopy

http://www.python.org/dev/peps/pep-0465/

New syntax: "c = a @ b" and "a @= b"

Includes a partial backport that works with the special methods at the Python level,
but not (properly) with extension types, which lack the necessary slot methods.  Also
currently lacks the subtype special casing that Python does for the numeric special
methods.

utility code construction for struct conversion requires constructing the field conversion functions as well

--HG--
extra : amend_source : af016229b6c8c40168070e4d3a9581ed12500d3f

utility code construction for struct conversion requires constructing the field conversion functions as well

--HG--
extra : transplant_source : %A3%81%87%E2%0A%20%DA%7D%7E%5B%A0%9B%80i%F9%8Az%9B%F3%DC

Compute each Makefile variable immediately

Otherwise the variables get re-computed over and over again every time
they are used, slowing things up.  Especially if someone adapts the
Makefile to several targets in their own real project. :)

revert to using codecs.open() for output files instead of io.open() as the latter cannot write str objects in text mode under Py2 (and we erroneously do that in some spots)

make encoding detection code a bit faster if the first two source file lines are longer than 250 bytes