[Test] Change FileTtest.MoveTest to use the temporary directory so it can be executed, without an access denied, on most environment (e.g. an iOS device)
[Test] Avoid MethodInfoTest.GetMethodBody failure when executed on a release (IL stripped) application on iOS
[Test] Avoid StackFrameTest.* failures when debugging symbols are not available (e.g. release configuration on iOS or Android)
[Test] Fix previous test change as the test is dependent on line numbers
[xbuild] Fix PCL 4.5 targets
[xbuild] Fix accidental local-copy of mscorlib

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[xbuild] Clean up some API to match .NET

Some .NET 4 API had leaked into .NET 2 builds.
[corlib] Remove unreliable test check
[corlib] Change AggregateException get base exception to not rely on base GetBaseException
[runtime] Fix the linux build.
[xbuild] Really don't local-copy mscorlib
ARM: Back up VFP scratch registers before using them on hard float.

This is because d0-d7 are argument registers and d8-d15 are
preserved registers - we can't use any of them as scratch
registers without restoring their previous values.
ARM: Handle large offsets in emit_float_args ().
ARM: Emit shorter floating point load/store sequences when possible.
[xbuild] Exists should be false for empty values

BXC17802 - xbuild evaluates Exist wrongly when the item group does not exist
Fix some warnings on mips32.
Fix another mips32 warning.
Fix some warnings on !MONO_ARCH_AOT_SUPPORTED targets.
[System] WebConnection and WebConnectionStream code cleanups.

* Merged WebConnection.EndWrite() and EndWrite2().

* WebConnectionStream.BeginWrite(): Use the same async-write
  callback for both chunked and non-chunked; remove the single-use
  small WriteRequestAsync() and inline it here to make the code
  more readable.

* WebConnectionStream.WriteRequestAsyncCB(): Now called for all
  async writes, call WebConnection.EndWrite() here.

The code is now more readable and easier to understand.  This is
the first part of a series of cleanups, which should eventually
lead towards full async and 100-continue.
Fixed time outs on http redirects

Fixed bug introduced by change 6ab86f50fd944b770ca388b478ce3cfb8b065647
where http request times out when it encounters a redirect.