Core: fixed ngx_write_chain_to_file() with IOV_MAX reached.
Core: fixed ngx_write_chain_to_file() with IOV_MAX reached.

Catched by dav_chunked.t on Solaris.  In released versions this might
potentially result in corruption of complex protocol responses if they
were written to disk and there were more distinct buffers than IOV_MAX
in a single write.

hy0kl/nginx,firebase/nginx,hy0kl/nginx,firebase/nginx,firebase/nginx,hy0kl/nginx,firebase/nginx