[runtime] Move thread attaching to mono-threads from the io-layer.
[runtime] Implement GetCurrentThreadId () using mono-threads.
[runtime] Rename the MONO_GSHARING define to ENABLE_GSHAREDVT for consistency.
Setup projects
Create meta assembly for Microsoft.Build.Engine
Update projects
Fix build (xbuild and MS.Build on XBUILD_12)
Move SolutionParser to Mono.XBuild.Engine and make it public
Move AssemblyLoadInfo to Mono.XBuild.Engine
Update projects
FIX public API of some Microsoft.Build.* dlls
Update projects
Add new assembly Mono.XBuild.Utilities
Setup and update projects
Add some deprecation warnings
Remove TaskItem from Microsoft.Build.dll build

It's not used anywhere. If someone needs it in the future they can pick up
its implementor Mono.XBuild.Utilities.TaskItemImpl from the
Mono.XBuild.Utilities assembly.
Rectify Microsoft.Build csproj file.
Add some files to MS.Build.Framework
Fix Microsoft.Build.csproj files
Update Microsoft.Build.Framework csproj files