Can't allow IOStream:set_max_buffer_size() to be set too low.
If the iostream buffer is set below TURBO_SOCKET_BUFFER_SZ
the socket could read more data than the max and would close
the stream erroneously.  This happened with the default 16K
header size now that the default TURBO_SOCKET_BUFFER_SZ was
increased to accomodate axTLS default read buffer size.
Add support for struct stat on 32-bit ppc architecture.
Switch back to using ffi.arch to define struct stat in cdef.lua
Update syscall.lua to support ppc 32-bit arch.
Switch back to using ffi.arch.
Oops..
Merge pull request #111 from jsolman/master

Max buffer size equals min size of axTLS buffer size. Change ABI to arch dependance for cdefs.