[system.data] BUGFIX: fixes issue with expression columns and IsNull:
 - bugzilla.xamarin.com issue 20925
 - if an expression column was added ayer there were rows, and then IsNull is called, the result is incorrect (it will always be true)
[system.data] Appended the fix to correct the whitespace Expression and argument checking
 - Whitespace Espressions:
 -- if a column expression is a pure whitespace, use an empty string instead
 -- if a column expression is surrounded by whitespace, preserve whitespace
 -- if a column expression is null/empty, use an empty string
 - Get a row's column value:
 -- make sure we throw exceptions if the column we are looking at is null
 -- make sure we throw exceptions if we can't find the column with the provided name
Fix several issues in System.Json

- Fix detection of extra characters in JSON input
- Fix detection of invalid negative numeric literals
- Disallow leading zeros
- Use "round-trip" format for floating point numbers
- Serialize NaN and Infinity as strings
- Use NumberFormatInfo.InvariantInfo for Convert.To*()
- Use standard number parsing methods in ReadNumericLiteral()
- Add test cases
ConnectCallback needs to call EndConnect

Socket.ConnectAsync uses BeginConnect, and ends here in
ConnectCallback. It needs to call EndConnect so any error can be
propagated up.

See Xamarin bug: https://bugzilla.xamarin.com/show_bug.cgi?id=21017
Fixes https://github.com/OfficeDev/Open-XML-SDK/issues/7 by allowing both relative and absolute urls
This change in released under the MIT license.
[mcs] Undo project changes from dedb33eadeb87ca80cb86f48e6fa47da882507e3 due to XS stupidity
[corlib] Fix test to not rely on compiler generated method
[mcs] Disable dedb33eadeb87ca80cb86f48e6fa47da882507e3 due to runtime bug
Fix enumeration values
Merge pull request #1152 from danielrh/hyperlink_package_parse

Fixes https://github.com/OfficeDev/Open-XML-SDK/issues/7 by allow absolute urls in relationships
Merge pull request #1148 from steffen-kiess/json

Fix several issues in System.Json
Merge pull request #1142 from edbprx/master

ConnectCallback needs to call EndConnect
Merge pull request #1132 from mattleibow/bugfix-20925

[system.data] BUGFIX: fixes issue with expression columns and IsNull:
Fixes https://github.com/OfficeDev/Open-XML-SDK/issues/6 by formatting core.xml date according to W3CDTF
This change in released under the MIT license.
[bcl] Fix retaining objects in one of the ConditionalWeakTable tests.
[corlib] Make CompletionOnDifferentCustomSynchronizationContext test more reliable
[corlib] Fix incorrect assert
[mcs] Extend intermediate value modification checks on generic value types
[runtime] Enable system aot when using --enable-loadedllvm, hopefully it works now.
Fix fallout from WebSocketMessageType change.

The WebSocketMessageType values were being used to send data over the
wire.  This is likely the reason why WebSocketMessageType had values
that were not compatible with .NET.