[FIX] Bug 267: wsdl fails with "Argument is out of range."

This fix bug 267
https://bugzilla.xamarin.com/show_bug.cgi?id=267

Signed-off-by: Etienne CHAMPETIER <etienne.champetier@fiducial.net>
When generating resources, it intends to add the .resources file to the FilesWritten list. However, it sets the ItemSpec on the wrong item, and a 'Clean' ends up deleting the .resx file.
Define GC_NOT_DLL for included boehm on win32.

This commit licensed as MIT/X11.
[xBuild] Support ToolsVersion 12

From VS2013, MSBuild is now decouple from the .NET Framework and is a separate redistributable. This means it has a new location and version numbering scheme. There are also some addition MSBuild properties because of this
[xBuild] Support use of properties defined in Choose elements in project references

This is used by the .fsproj files generated by VS2013 which use a Choose element to set the location of the F# targets file to import
[xBuild] Suport >= in string conditions

e.g: '$(MSBuildAssemblyVersion)' == '' and ('$(VisualStudioVersion)' != '' and '$(VisualStudioVersion)' >= '12.0'), used in the .targets files shipped with VS2013
[xBuild] Support for ImportGroup element

Used in the .targets files shipped with VS2013
[xBuild] Fix Import elements with the combination of wildcards and absolute paths

Used in the .targets files shipped with VS2013
[xBuild] Fix compilation for Mono 2.0
[xBuild] Fix use of properties in project references when those properties use MSBuildExtensionPath after expanded
[xBuild] Add missing VisualStudioVersion propety which was introduced in VS2012
[xBuild] Don't set any VisualStudioVersion
Adjust defines to check for 4_0 instead of 3_0
Makefile magic ...
[aot] Only use an AOT shortcut in the trampoline code if its safe to do so. Fixes #15345.
[PCL]: Update the PCL Facade Assemblies.
[sgen] Don't crash on nurseries of 512M or larger.
Dummy test commit.
Fixes too early optimization of binary &&/& bool constants. Fixes part of #15392
Better check for open generic types in probing expression. Fixes #15422