revert to using malloc/free for data buffer allocation in case external code wants to fiddle with it

make it easier for the C compiler to prune some useless error checking code in cython.array constructor

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extra : amend_source : 4d5d9dc96421710652afe8614c9f32db26cc88c1

--HG--
extra : amend_source : 685e555a2102e496280287b3b7605d67d694ff40

use CPython heap memory allocation for memory views where possible (outside of nogil sections) as it tends to be faster than plain malloc()

--HG--
extra : amend_source : 8ea50b285fc8d55899450c179754d7c2aba94591

some minor changes

fix deprecated imports in "Unicode and passing strings" tutorial

make reference from memory allocation tutorial to memory views and array.array support more prominent

get rid of __signature__ property for cyfunctions again as inspect.py in Py3.4 can do the same thing more efficiently all by itself now (only commenting it out because it could potentially become a feature again at some point)

Allow docstrings on cdef classes in .pxd files