Log Message:
py-cffi: updated to 1.13.0

v1.13
* ffi.from_buffer("type *", ..) is now supported, in addition to
  "type[]".  You can then write p.field to access the items, instead
  of only p[0].field.  Be careful that no bounds checking is performed, so
  p[n] might access data out of bounds.
* fix for structs containing unnamed bitfields like int : 1;.
* when calling cdata of "function pointer" type, give a RuntimeError \ 
instead
  of a crash if the pointer happens to be NULL
* support some more binary operations between constants in enum definitions
* silence a warning incorrectly emitted if you use a quote in a preprocessor
  line
* detect a corner case that would throw the C code into an infinite
  recursion, with ffi.cdef("""struct X { void(*fnptr)(struct X); \ 
};""")