Added (libevent,tor) and modified glibc-compat

ports/libevent/README

+This is a port of libevent (an event notification library) to nacl platfrom.
+For details visit : http://libevent.org
+
+The library is "functional" albeit with some issues, this documents lists and
+keep tracks all those.
+
+Issue #1
+Callbacks due to signals are NOT supported.
+Reason: nacl.io do not support POSIX signals.
+Details : sigaction(...) and signal(...) are not(yet) implemented on nacl.io,
+thus the calls evsignal_add,evsignal_del,evsignal_pending should be avoided,
+also event_add/event_del when passed with EV_SIGNAL will also fail.
+
+For details about these functions visit :
+http://www.wangafu.net/~nickm/libevent-book/Ref4_event.html
+
+See /samples/hello-world.c for more details.
+To check if everything is working fine, run hello-world.nexe in nacl-devenv
+extension and point your browser to localhost:9995 and you should see "hello
+world".
+
+To debug/see implementation
+Look for /event.c, /signal.c and /evmap.c
+In /signal.c see function _evsig_set_handler and _evsig_restore_handler
+
+Typical function call
+event_add > event_add_internal > (if signal) evmap_signal_add > evsig_add
+
+Issue #2
+Post build tests are skipped.
+Reason : setitimer and getitimer not available in newlib.
+
+Issue #3
+Build against glibc is not functional, ie either static linking fails or
+sometimes ELF header error pops up
+Reason : unknown (issue deprioritized)
+
+Note
+1.Code in /samples/ (except hello-world.c) is not yet tested (or not yet
+modified to work on nacl platform)
+2.Libevnt uses socketpair(...) extensively, however the same is not
+implemented on nacl, thus custom implementation is used, to see details
+look for evutil_ersatz_socketpair(...) in /evutil.c