CPython: remove excess initializer elements

lmdb/cpython.c:1229: warning: excess elements in struct initializer
lmdb/cpython.c:1229: warning: (near initialization for ‘arg’)
lmdb/cpython.c:1229: warning: excess elements in struct initializer
lmdb/cpython.c:1229: warning: (near initialization for ‘arg’)
CPython: don't redefine PyBUF_READ

I think this was for 2.5.

lmdb/cpython.c:223:1: warning: "PyBUF_READ" redefined
CPython: cure some truncation warnings

lmdb/cpython.c: In function ‘parse_arg’:
lmdb/cpython.c:780: warning: implicit conversion shortens 64-bit value
into a 32-bit value
lmdb/cpython.c:785: warning: implicit conversion shortens 64-bit value
into a 32-bit value
lmdb/cpython.c: In function ‘parse_arg’:
lmdb/cpython.c:780: warning: implicit conversion shortens 64-bit value
into a 32-bit value
lmdb/cpython.c: In function ‘parse_args’:
lmdb/cpython.c:810: warning: implicit conversion shortens 64-bit value
into a 32-bit value
lmdb/cpython.c:827: warning: implicit conversion shortens 64-bit value
into a 32-bit value
lmdb/cpython.c: In function ‘env_new’:
lmdb/cpython.c:1276: warning: implicit conversion shortens 64-bit value
into a 32-bit value