Unconditionally use XmlTextReader
Unconditionally use XmlTextReader

Works around a behavior difference between XmlReader and XmlTextReader
that caused newlines in attributes to be ignored in command-line builds.

Fixes #4210.

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