Changes to the C code to compile under Python 2.6
Changes to the C code to compile under Python 2.6

Changes I was working on using a branch. This almost compiled on
Python 2.7 as well with manual change to avoid clashing definitions
of PyErr_NewExceptionWithDoc

peterjc/backports.lzma,r3m0t/backports.lzma,peterjc/backports.lzma