Test WebClient.UploadFileTaskAsync ContentType. Covers 19529.
TimeZoneInfo is now always present in corlib.
Prior to net_4_0 TimeZoneInfo is a private class.
CurrentSystemTimeZone.GetUtcOffset now supports multiple DST periods.
DateTime.Now was returning wrong values when system TimeZone had more than one daylight saving time.
Fixes 22648.
Removed unused CurrentSystemTimeZone fields and methods.
Updated TimeZoneInfoTest.DSTTransisions to correct .NET behavior.
Test TimeZoneInfo.GetUtcOffset with multiple DST and DateTimeKind.
Simplified TimeZone.ToLocalTime.
Old code was producing invalid DST dates.
ConvertTimeToUtc no longer relies in DateTime.ToUniversalTime.
Removed repeated logic from TimeZoneInfo.ConvertTimeToUtc.
Created helper method TimeZoneInfo.IsInDST.
TimeZoneInfo.GetUtcOffset now handles all DateTimeKinds.
Removed GetUtcOffset cohesion with TimeZoneInfo.IsDaylightSavingTime.
TimeZoneInfo.IsDaylightSavingTime now uses GetUtcOffset.
Refactored TimeZoneInfo.GetUtcOffset.
Added GetUtcOffset auxiliar methods with bool out parameter that is true when the given DateTime is a DST.
Use TZ transitions when AdjustementRules are ignored. Fixes 23170.
In some cases the timezone transitions provided by iOS are not convertible to AdjustmentRules because of changes on the base offset.
Now we store the transitions so they can be used instead of an incomplete list of AdjustmentRules.
Added bash script to test DateTime.Now.
The test changes TZ environment variable and compares DateTime.Now with system date.
The test checks all the timezones installed in /usr/share/zoneinfo/.
TimeZoneInfo.CreateLocal now handles environment variable TZ.
Call SetupRequestAsync only after ContentType changes. Fixes 19529.
Reset stream position before doing CopyToAsync.
CopyToAsync begins copying at the current position.
[CI] Add appveyor.yml configuration file to support Windows build

Adds a configuration file to facilitate build of Mono with Cygwin
on Appveyor Windows-based build workers.

Dependencies are installed on a clean Appveyor build image for
each build and the result of the 'make install' step is stored
as a build output 'artifact' for further testing or deployment.

Signed-off-by: Alex J Lennon <ajlennon@dynamicdevices.co.uk>
Fix for ObjectDiposedException in DispatcherCB class

https://bugzilla.xamarin.com/show_bug.cgi?id=23700