Remove ItemExpressionCapture.SeparatorLength
Remove ItemExpressionCapture.SeparatorLength

It's not consumed by anyone and increases size of the class.

AndyGerlicher/msbuild,chipitsine/msbuild,mono/msbuild,mono/msbuild,jeffkl/msbuild,chipitsine/msbuild,mono/msbuild,sean-gilliam/msbuild,AndyGerlicher/msbuild,cdmihai/msbuild,rainersigwald/msbuild,jeffkl/msbuild,sean-gilliam/msbuild,chipitsine/msbuild,AndyGerlicher/msbuild,Microsoft/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,rainersigwald/msbuild,rainersigwald/msbuild,chipitsine/msbuild,cdmihai/msbuild,jeffkl/msbuild,Microsoft/msbuild,sean-gilliam/msbuild,Microsoft/msbuild,mono/msbuild,cdmihai/msbuild,cdmihai/msbuild,Microsoft/msbuild,jeffkl/msbuild,AndyGerlicher/msbuild