unbound methods/classmethods use PyMethodObject in Py3 as well, so include them in method call optimisation

If cppclass is redefined, make sure the this pointer enters the correct scope

fix test: passing an object into a METH_O Python function no longer stores it in a tuple and thus no longer increases its refcount

fine tune method call optimisation to mark likely plain function calls explicitly as unlikely() for the C compiler

enable method call optimisation on all simple Python calls as PyMethod_Check() should be cheap enough

avoid performance regression in one-arg calling case if the function turns out to be not a method at runtime

streamline method call optimisation a bit more by freeing method object as early as possible to put it back into CPython's freelist for quick reuse

The previous commit reveals too much information about the system.  With
this change only modules of the processed package are expanded.  The
expanded path reaches no deeper than the package's root.

The table of file names written to the c or cpp file contains absolute
file paths.  This affects, in particular, profiling.  The c method
__pyx_TraceCall takes as one of its arguments a file name, which will be
read from the table of file names.

replace PyMapping_Keys() usage by safer code (PyMapping_Keys() may return a tuple, but we try to sort it as a list afterwards)

streamline non-C-function fallback code for the 1-arg call case to avoid overhead beyond the type checks

simplify WithTargetAssignmentStatNode and make it more robust against replacements of the context manager node; undo node.result() checking as it broke TempNode's disposal code

when replacing SimpleCallNode with PyMethodCallNode, make sure we replace all cloned references to the node, not only the current one