Export .isSeriesLocked() API function

This is a followup to https://github.com/danvk/dygraphs/pull/159,
exposing the .lockedSet_ internal attribute through the API
for use in callbacks, and also with an eye for future extraction
of the mouseover logic into a plugin.

Includes a fix for the auto_test name, it was erroneously replacing
the existing testClosestPointCallbackCss1 test due to a name clash.
Stepplot and errorbars sync fix

The 1st error bar wasn't been drawn on stepplots, instead the script started with drawing the horizontal line of the 2nd error bar which was then shown under the 1st value, the 3rd error bar was drawn under the 2nd value, etc, what resulted in an incorrect graph.

Demo:

Without the fix:
http://wimme.net/temp/dygraphs1/index.htm
http://wimme.net/temp/dygraphs1/weather.htm
Notice how the error bars and the line charts are not in sync, the error bar is one value ahead

With the fix:
http://wimme.net/temp/dygraphs2/
http://wimme.net/temp/dygraphs2/weather.htm
Here are the error bars and the line charts nicely in sync, the way it should be.
Merge pull request #164 from wimme/patch-3

Stepplot and errorbars sync fix
Fix & regression test for Issue 358:857a6931 breaks stacked graph highlighting
failing test for iframe mouseup
Fix Issue 361: Moving the mouse over an iframe breaks range selector interaction
Fix issue 201:zero-series test broken
rv f4e7e19, which was committed by accident
Fix issue 139:set fill option by series rather than for entire graph
update docs to reflect that fillGraph is now per-series.
Fix Issue 328:Thick data lines shown breaks
Fix Issue 359:animatedZooms option has a bad interaction with range selector
verify that issue 185 is fixed
resolve issue 180 via better documentation
Fix Issue 229:valueRange and errorBars not mixing when valueRange max = data max
add auto_test from Issue 242
Fix Issue 162: Support DOS-style line endings
small script to track compressed file sizes
Remove variable re-definitions
Merge branch 'master' of github.com:danvk/dygraphs