improve detection of the extension suffix for cython_inline

reliance on imp.get_suffixes()[0] broke cython_inline on Debian systems
with support of multiarch where the first entry corresponded to the multiarch
suffix while distutil were using non-multiarch version while actually building
the extension

Reference: http://mail.python.org/pipermail//cython-devel/2012-July/002933.html

Now it would cache the suffix used by distutils and reuse it within the
session

cpython.type: Add ctypedef for `__builtin__.type`

moved method dispatcher implementation from OptimizeBuiltinCalls class into new MethodDispatcherTransform class in Visitor.py to enable reuse

rewrite of sliced char* decoding as utility functions, implemented efficient sliced decoding for C++ std::string

--HG--
extra : rebase_source : e134f5595be98eb990ab2195e8208940efb171fe

Fix "missing cimport: ... cython" warning.