Log Message:
(math/R-xts) Updated 0.12.1 to 0.12.2

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Changed in xts 0.12.2:

o `Ops.xts()` no longer changes column names (via `make.names()`) when the two
  objects do not have identical indexes. This makes it consistent with
  `Ops.zoo()`. (#114)

o Subsetting a zero-length xts object now returns an object with the same
  storage type as the input. It previously always returned a 'logical' xts
  object. (#376)

o `tclass()` and `tzone()` now return the correct values for zero-length xts
  objects, instead of the defaults in the `.xts()` constructor. Thanks to Andre
  Mikulec for the report and suggested patch! (#255)

o `endpoints()` now always returns last observation. Thanks to GitHub user
  Eluvias for the report. (#300)

o Ensure `endpoints()` errors for every 'on' value when `k < 1`. It was not
  throwing an error for `k < 1` for `on` of "years", \ 
"quarters", or "months".
  Thanks to Eluvias for the report. (#301)

o Fix `window()` for yearmon and yearqtr indexes. In xts < 0.11-0, `window.zoo()`
  was dispatched when `window()` was called on a xts object because there was no
  `window.xts()` method. `window.zoo()` supports additional types of values for the
  `start` argument, and possibly other features. So this fixes a breaking change
  in xts >= 0.11-0. Thanks to GitHub user annaymj for the report. (#312)

o Clarify whether `axTicksByTime()` returns index timestamps or locations (e.g.
  1, 2, 3). Thanks to @ggrothendieck for the suggestion and feedback. (#354)

o Fix merge on complex types when 'fill' is needed. `merge()` would throw an
  error because it treated 'fill' as double instead of complex. Thanks to
  @ggrothendieck for the report. (#346)

o Add a message to tell the user how to disable 'xts_check_TZ' warning. Thanks
  to Jerzy Pawlowski for the nudge. (#113)

o Update `rbind()` to handle xts objects without dim attribute. `rbind()` threw
  an obscure error if one of the xts objects does not have a dim attribute. We
  can handle this case even though all xts objects should always have a dim
  attribute. (#361)

o `split.xts()` now always return a named list, which makes it consistent with
  `split.zoo()`. Thanks to Gabor Grothendieck for the report. (#357)

o xts objects with a zero-length POSIXct index now return a zero-length POSIXct
  vector instead of a zero-length integer vector. Thanks to Jasper Schelfhout
  for the report and PR! (#363, #364)

o Add suffixes to output of `merge.xts()`. The suffixes are consistent with
  `merge.default()` and not `merge.zoo()`, because `merge.zoo()` automatically
  uses "." as a separator between column names, but the default method \ 
doesn't.
  Thanks to Pierre Lamarche for the nudge. Better late than never? (#38, #371)

Changes to plotting functionality
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o You can now omit the data time range from the upper-right portion of a plot
  by setting `main.timespan = FALSE`. (#247)

o Fix `addEventLines()` when plotted objects have a 'yearmon' index. The ISO-8601
  range string was not created correctly. Thanks to @paessens for the report.
  (#353)

o Make 'ylim' robust against numerical precision issues by replacing `==` with
  `all.equal()`. Thanks to @bollard for the report, PR, and a ton of help
  debugging intermediate solutions! (#368)

o Series added to a panel now extend the panel's y-axis. Previously the y-axis
  limits were based on the first series' values and not updated when new series
  were added. So values of the new series did not appear on the plot if they
  were outside of the original series' min/max. Thanks to Vitalie Spinu for the
  report and help debugging and testing! (#360)

o All series added to any panel of a plot now update the x-axis of all panels.
  So the entire plot's x-axis will include every series' time index values
  within the original plot's time range. This behavior is consistent with
  `chart_Series()`. Thanks to Vitalie Spinu for the report and help debugging
  and testing! (#360, #216)

o All y-values are now plotted for series that have duplicate index values, but
  different data values. Thanks to Vitalie Spinu for the report and help
  debugging and testing! (#360)

o Adding a series can now extend the x-axis before/after the plot's existing
  time index range, so all of the new series' time index values are included in
  the plot. This is FALSE by default to maintain backward compatibility. Thanks
  to Vitalie Spinu for the report and help debugging and testing! (#360)