[MWF] Disable DataRemainsOnClipboard_Xamarin4959 test.

It works fine on a regular system but breaks under Xvfb.

http://monojenkins.cloudapp.net/job/Mono/230/testReport/MonoTests.System.Windows.Forms/ClipboardTest/DataRemainsOnClipboard_Xamarin4959/
[runtime] Define DEFFILEMODE to 0666 if not defined.
[runtime] Make it possible to create views to magic zero size files such as /dev/zero. Fixes #19460
[runtime] Fix error handling with named memory regions.
[runtime] Rework named mapping to use an unlinked file to provide correct mapping semantics.

Instead of using mono_valloc we create a temp file and unlink it. With this we can have the right
mmap semantics regarding CoW and access rights.

This does simplify the code too by completely removing the mapping kind.
Added test for bug #20672 (fixed in aeab5b59021f4a712d54357c8bbeaa6fac12dc37)
[MWF] Disable OneIdlePerThread test.

The code that made this test work was reverted, so this test is
bound to fail randomly.
Merge pull request #1113 from akoeplinger/fix-cache-test

[System.Runtime.Caching] Fixed test that failed intermittently on slow systems
Silence a warning in file-mmap-posix.c.
Fix the build.
[Managed.Windows.Forms] Verify that DataMember is valid when setting DataSource

When DataMember is already set before DataSource we need to verify that it refers to a valid property in the DataSource setter, otherwise we'd get an exception in ResetList ().
This fixes the following failing tests: BindingSourceTest.DataMemberBeforeDataSource and BindingSourceTest.DataSourceAssignToDefaultType.

Commit licensed under MIT/X11.
[System.Net] Do not assume IPv6 is enabled in UdpClientTest

Without this, three of the tests fail on Linux kernels without IPv6
support.

This is a minimal fix, copy'n'pasting a conditional which was used in
other tests.  It might be nicer to factor out the SupportsIPv6 to its
own utility function.
Merge pull request #1117 from akoeplinger/fix-databindingsource

[Managed.Windows.Forms] Verify that DataMember is valid when setting DataSource
[llvm] Remove a small source workaround which is no longer needed.
[Managed.Windows.Forms] Revert a revert commit that accidentally changed the wrong code

When the commit 8334fe3a56c978ffe7f8cb199536f9b3234afdbe was reverted in a791cfc1640bec442757f78fe71e428d643e90ed, accidentally the wrong chunk of code was changed.

This commit reverts the changes correctly.
[Managed.Windows.Forms] Added more asserts to the CurrencyManagerTest2 test

These were useful while investigating 4b50211fb7f1dd2621673edd100f30eb39098d7d
[llvm] Update the LLVM backend to llvm ca4e226df2e13a9e87376a880035efa376639c98.
Merge pull request #1119 from akoeplinger/fix-currencymanager

 [Managed.Windows.Forms] Revert a revert commit that accidentally changed the wrong code
Merge pull request #1118 from kitsilanosoftware/udp-client-test-check-ipv6

[System.Net] Do not assume IPv6 is enabled in UdpClientTest
libmonoutils: Removed need for X64 MASM definition
Check for availability of the RAX register, checking if we're running x64