Make generator common code depend only upon constants.

Make generator common code depend only upon constants.

It turns out that we don't have to set $state to machineEndState, since
$GState already guards against $moveNext being inadvertently called after
generator end.

BUG=None
TEST=None

[usrbincc, 2013-03-13 21:56:01]

Patch order at a glance:

Make generator common code depend only upon constants.
https://codereview.appspot.com/7761043
Use generator 'return' to simplify the code for 'close()'
https://codereview.appspot.com/7519046
Checking undefined properties is slow, so cache in a boolean.
https://codereview.appspot.com/7663044
Use an inner object instead of captured vars.
https://codereview.appspot.com/7547045
Minimal diff for converting generator interface wrap to a function.
https://codereview.appspot.com/7547046
Use RuntimeInliner to provide the generator common code.
https://codereview.appspot.com/7487046

I tried to keep each patch as small as possible, while still having each
be self-contained. To keep the diffs readable, I didn't do any
reindenting.

If you're strapped for time, we can probably just postpone the repl
patches indefinitely. These patches are most easily applied prior to
changing the iterator protocol, so I'm hoping to get them looked at
before doing anything in that direction.

#--cut--
dl_check() {
  local f=$(basename $1)
  test -e $f || curl -sO $1
  openssl sha1 < $f | grep -q "= $2" && return 0
  echo sha1 mismatch!
  return 1
}

git checkout dbaacc7efc9fd56b   # recent HEAD for branch master

git checkout -b issue7487046-generator-common-code

### Make generator common code depend only upon constants.
dl_check https://codereview.appspot.com/download/issue7761043_1.diff \
  59f4303fdcef4108 && git apply issue7761043_1.diff && make test

### Use generator 'return' to simplify the code for 'close()'
dl_check https://codereview.appspot.com/download/issue7519046_1.diff \
  fee7c25fbc0f1781 && git apply issue7519046_1.diff && make test

### Checking undefined properties is slow, so cache in a boolean.
dl_check https://codereview.appspot.com/download/issue7663044_1.diff \
  8d7907018eb0e7fa && git apply issue7663044_1.diff && make test

### Use an inner object instead of captured vars.
dl_check https://codereview.appspot.com/download/issue7547045_1.diff \
  6a09361dfac60156 && git apply issue7547045_1.diff && make test

### Minimal diff for converting generator interface wrap to a function.
dl_check https://codereview.appspot.com/download/issue7547046_1.diff \
  ffd57a8508df7210 && git apply issue7547046_1.diff && make test

### Use RuntimeInliner to provide the generator common code.
dl_check https://codereview.appspot.com/download/issue7487046_2001.diff \
  cd55070593097f0c && git apply issue7487046_2001.diff && make test
#--cut--

[arv, 2013-03-13 22:13:07]

LGTM