Fix the date time set in file by removing the ':'.

This is the same code than the one under SendCore. The date time should
not have the : (time zone offset) to be able to use the file.
[Mono.Parallel] Removed broken Mono.Threading.Tasks code

The code in MonoTaskExtensions.cs relied on the internal method Execute(Action<Task>) in System.Threading.Tasks.Task which was removed in 0a66e60.
Added stress test to ConcurrentQueue.TryPeek.
The test checks that in some race condition the queue does not return null.
Changed TryPeek to handle race condition with Dequeue.
Dequeue sets the head.Value to its default. When TryPeek is interrupted in the process of retrieving the value some times Dequeue sets the value to its default. TryPeek now checks the head has not been changed before returning the value.
[System] Fix WebClientTest build in net_2_0.

CancellationTokenSource is a 4.0 thing.
[msbuild] Implemented instance members on static property evaluation
[mcs] null coalescing operator cannot reduce constants
Test JavaScriptSerializer.Deserialize with nullable enums. Covers #19287.
Improved JavaScriptSerializer.ConvertToType Nullable handling. Fixes #19287. ConvertToType was returning null even when the object was not a string. When the target type is Nullable, ConvertToType returns null if the object is an empty string, if the object is not a string and the target type is obtainable from a string then the object is converted to a string and the string to the target type.
Merge pull request #1082 from esdrubal/bug19287

Improved JavaScriptSerializer.ConvertToType Nullable handling. Fixes #19287.
[mcs] Don't wrap enum constants during folding when result is reduced
[mcs] Add more checks to dynamic logical operations when lhs is not of dynamic type
Architectural level set to z10 instruction set
Fix s390x soft debug
Correct op_seqpoint length
[mcs] Emit result type conversion for null coalescing operator on nullable type
[mcs] Better error message for attribute value used for unsupported parameter type
Fixes build
[mcs] Revert unwanted change from 9e5d5e5c90fce0374447b81111b5d6b08773c55a
fix win thread size calc.