fixes http://code.google.com/p/gevent/issues/detail?id=92

this makes the code a bit cleaner and it's easier to check if we're
using readline in _do_read. we need to do that in order to check for
short post requests.

this contains some failing tests for truncated post requests
(http://code.google.com/p/gevent/issues/detail?id=92)

we exercise the Input class without going through the complete WSGI
toolchain.

this makes test__execmodules.py succeed. while I'm here, also hide the
_pywsgi name.

do not use the current globals() as namespace, rather setup a clean
namespace inside a newly created __main__ module.

the missing "import sys" in test__socket_timeout.py fixed two commits
ago, wouldn't go unnoticed with this change.

Otherwise I'm always confused for a minute until I remember to run
"python testrunner.py"

see http://code.google.com/p/gevent/issues/detail?id=93 for more information

see http://code.google.com/p/gevent/issues/detail?id=93 for more information.

do not sort the results of getaddrinfo() because the order is actually important here

pywsgi: if we failed to send the reply, change 'status' to socket error so that the logs mention the error

wsgiserver.py: rename 'hello_world' to 'application'; only start server if run as a script (so that it can also be run by another server)

gevent.signal: spawn Greenlet instead of raw greenlet; switch into the greenlet immediatelly when the signal handler is called

start() no longer raises an exception if Greenlet was already started. it also now does nothing if the greenlet already exited (previously it would schedule another switch)