Backport of PEP 3101, Advanced String Formatting, from py3k. Highlights: - Adding PyObject_Format. - Adding string.Format class. - Adding __format__ for str, unicode, int, long, float, datetime. - Adding builtin format. - Adding ''.format and u''.format. - str/unicode fixups for formatters. The files in Objects/stringlib that implement PEP 3101 (stringdefs.h, unicodedefs.h, formatter.h, string_format.h) are identical in trunk and py3k. Any changes from here on should be made to trunk, and changes will propogate to py3k).