Remove excessive shortcut key matching in ToolStrip

This fixes https://bugzilla.xamarin.com/show_bug.cgi?id=23532.
Fix potential crash in ListView.ItemControl.ItemsMouseDown

This fixes Xamarin bug 23591.  Side-effects of internal processing of
ItemsMouseDown can cause ItemsMouseUp before ItemsMouseUp has finished.
Improved support for TimeZoneInfo under windows.

When cross compiling with gcc, LIBC is defined and
thus never checks the registry for the timezone information.

This change is released under the MIT license.
Fix bugs in sizing TableLayoutPanel (Xamarin bug 18638)

Consider spans and absolute sizes in computing PreferredSize for
TableLayoutPanel.
Also fix bug in allocating unused width to SizeType.Absolute columns.

Change-Id: Ic5065b83ced8195d1c5be39087f33b0d632fc9a6
Change bootstrap profile to target 4.0 framework. Bump system mono requirement to version 3.2 at least
[xbuild] Update another default tools setting
[sgen] Remove `SGEN_HAVE_CONCURRENT_MARK`.

We always have concurrent mark.
Fixed System.IO.Compression.FileSystem.ZipFile.CreateFromDirectory overload to use compressionLevel.
Fixed incorrect markdown syntax for two links
Merge pull request #1438 from jonorossi/patch-1

Fixed incorrect markdown syntax for two links
Merge pull request #1437 from jonorossi/io_compression_fs_fix

Fixed ZipFile.CreateFromDirectory overload to use compressionLevel
Merge pull request #1410 from alesliehughes/master

Improved support for TimeZoneInfo under windows.
[System.Core] Bring .NET implementation of ReaderWriterLockSlim.
[System.Core] Removed no longer used files.
System.Core is now using .NET implementations of LockRecursionPolicy and ReaderWriterLockSlim.
[mscorlib/Android] Support TimeZoneInfo.FindSystemTimeZoneById("Local")

Fixes: https://bugzilla.xamarin.com/show_bug.cgi?id=24741

Xamarin.Android didn't previously support
TimeZoneInfo.FindSystemTimeZoneById("Local") because of oversight (and
overly nested #if conditionals).

Compare `id` against "Local" *before* doing platform-specific
codepaths so that finding the "Local" TimeZone works as expected on
Xamarin.Android, and merge the `#if MONODROID` with the existing code.
Fix make dist if boehm is disabled.
Fix a bunch of warnings in the runtime code.
[bcl] Remove all uses of Thread.Volatile{Read,Write}.

These methods are broken, misleading, and generally harmful. Always prefer the
`Volatile` class over these to make intent clear and to get sensible semantics.

http://blog.alexrp.com/2014/03/30/dot-net-atomics-and-memory-model-semantics/
[runtime] Added missing else branch setting il_offset to -1.
[msvc] Fixed missing semi-colon.