Fixes #318.

There are a few kinds of errors that are very confusing.
1. Errors raised in nextTick
2. Errors emitted on the "error" event
3. RangeErrors that crash the program (or anything without a stack trace)

Long traces will make make these better, of course.  In the meantime, this
adds a few handy signposts (in the form of better error reporting and
comments on the otherwise inscrutable code printed to the terminal) that can
help new users find the cause, or at least, ask for help more effectively.

HTTP/1.1 requests, either with an event (check_continue) or automatically, if no event handler is present.

Add client-side expect/continue support, tests.

Expound upon client requirements for expect/continue.

Thanks to Tim Becker for pointing this out.

Reported here:
http://groups.google.com/group/nodejs-dev/browse_thread/thread/9e063d0938f99879

Would be good to test this somehow...

Reported by Kadir Pekel <kadirpekel@gmail.com>

Made this test in response to this thread:
http://groups.google.com/group/nodejs/browse_thread/thread/f82835007a277de2/
But Node appears to be working correctly.

New() methods should be invoked as constructors, not regular functions.
Corner cases like Script::New() may cause a SIGSEGV when the GC is run.

More details: http://groups.google.com/group/nodejs/browse_thread/thread/a7e5db68d4cd6356