Make TreeFragment.py more readable; copy substitution nodes and copy over pos attributes on substitutions

Some changes in class hierarchies etc.; transforms no longer has a common
base class and VisitorTransform is a subclass of TreeVisitor rather than
the reverse. Also removed visitor use of get_child_accessors;
child_attrs is accessed directly (because of claims of overengineering :-) ).

--HG--
rename : Cython/Compiler/Transform.py => Cython/Compiler/Visitor.py

invalidate the cache of all subtypes when updating a type's tp_dict (algorithm copied from typeobject.c in Py3)

--HG--
rename : tests/run/docstrings.pyx => tests/compile/docstrings.pyx

--HG--
rename : tests/run/classmethod.pyx => tests/run/staticmethod.pyx

--HG--
rename : tests/broken/arraytoptrarg.pyx => tests/compile/arraytoptrarg.pyx
rename : tests/broken/ass2longlong.pyx => tests/compile/ass2longlong.pyx
rename : tests/broken/builtinfuncs.pyx => tests/compile/builtinfuncs.pyx
rename : tests/broken/cascmp.pyx => tests/compile/cascmp.pyx
rename : tests/broken/cassign.pyx => tests/compile/cassign.pyx
rename : tests/broken/casttoexttype.pyx => tests/compile/casttoexttype.pyx
rename : tests/broken/cnamespec.pyx => tests/compile/cnamespec.pyx
rename : tests/broken/cnumop.pyx => tests/compile/cnumop.pyx
rename : tests/broken/cunsignedlong.pyx => tests/compile/cunsignedlong.pyx
rename : tests/broken/del.pyx => tests/compile/del.pyx
rename : tests/broken/delslice.pyx => tests/compile/delslice.pyx
rename : tests/broken/drake1.pyx => tests/compile/drake1.pyx
rename : tests/broken/eqcmp.pyx => tests/compile/eqcmp.pyx
rename : tests/broken/ewing1.pyx => tests/compile/ewing1.pyx
rename : tests/broken/ewing5.pyx => tests/compile/ewing5.pyx
rename : tests/broken/excvalcheck.pyx => tests/compile/excvalcheck.pyx
rename : tests/broken/excvalreturn.pyx => tests/compile/excvalreturn.pyx
rename : tests/broken/extcoerce.pyx => tests/compile/extcoerce.pyx
rename : tests/broken/extdescrdel.pyx => tests/compile/extdescrdel.pyx
rename : tests/broken/extdescrget.pyx => tests/compile/extdescrget.pyx
rename : tests/broken/extdescrset.pyx => tests/compile/extdescrset.pyx
rename : tests/broken/extexttype.pyx => tests/compile/extexttype.pyx
rename : tests/broken/extgetitem.pyx => tests/compile/extgetitem.pyx
rename : tests/broken/extinheritdel.pyx => tests/compile/extinheritdel.pyx
rename : tests/broken/extinheritset.pyx => tests/compile/extinheritset.pyx
rename : tests/broken/extpropertyall.pyx => tests/compile/extpropertyall.pyx
rename : tests/broken/extpymemberdef.pyx => tests/compile/extpymemberdef.pyx
rename : tests/broken/forfromelse.pyx => tests/compile/forfromelse.pyx
rename : tests/broken/gencall.pyx => tests/compile/gencall.pyx
rename : tests/broken/globalstmt.pyx => tests/compile/globalstmt.pyx
rename : tests/broken/gustafsson2.pyx => tests/compile/gustafsson2.pyx
rename : tests/broken/index.pyx => tests/compile/index.pyx
rename : tests/broken/jiba5.pyx => tests/compile/jiba5.pyx
rename : tests/broken/jiba6.pyx => tests/compile/jiba6.pyx
rename : tests/broken/johnson1.pyx => tests/compile/johnson1.pyx
rename : tests/broken/magcmp.pyx => tests/compile/magcmp.pyx
rename : tests/broken/none.pyx => tests/compile/none.pyx
rename : tests/broken/notnonearg.pyx => tests/compile/notnonearg.pyx
rename : tests/broken/r_pernici1.pyx => tests/compile/r_pernici1.pyx
rename : tests/broken/slicex.pyx => tests/compile/slicex.pyx
rename : tests/broken/traceback.pyx => tests/compile/traceback.pyx
rename : tests/broken/watts2.pyx => tests/compile/watts2.pyx
rename : tests/broken/anonymousenum.pyx => tests/run/anonymousenum.pyx
rename : tests/broken/ass2cglobal.pyx => tests/run/ass2cglobal.pyx
rename : tests/broken/cstringmeth.pyx => tests/run/cstringmeth.pyx
rename : tests/broken/extcmethod.pyx => tests/run/extcmethod.pyx
rename : tests/broken/extpropertyref.pyx => tests/run/extpropertyref.pyx
rename : tests/broken/filenames.pxi => tests/run/filenames.pxi
rename : tests/broken/filenames.pyx => tests/run/filenames.pyx
rename : tests/broken/inhcmethcall.pyx => tests/run/inhcmethcall.pyx
rename : tests/broken/king1.pyx => tests/run/king1.pyx
rename : tests/broken/menten1.pyx => tests/run/menten1.pyx
rename : tests/broken/nononetypecheck.pyx => tests/run/nononetypecheck.pyx
rename : tests/broken/tandemstats.pyx => tests/run/tandemstats.pyx
rename : tests/broken/watts1.pyx => tests/run/watts1.pyx