use uname(2) instead of /proc/, this allows to run nginx in chroot

r1682, r1683 merge:

typo and style fixes

Cygwin support

avoid segfault if poll is used and endless loop if select is used

fix English grammar

style fix: remove double semicolons

make 64-bit ngx_int_t on 64-bit platforms

destroy ngx_cycle->pool on exit

win32 ngx_is_exec() stub

set worker_priority, worker_rlimit_nofile, worker_rlimit_core, and
worker_rlimit_sigpending without super-user privileges testing