VS: connect /Y- compiler option with "Not Using Precompiled Headers"
The change allows to selectively disable PrecompiledHeaders.
Despite the $(VCTargetsPath)/1033/cl.xml
contains an empty value for switch,
for effectively turn off setting need to use /Y- option as described on msdn:
https://msdn.microsoft.com/en-us/library/1hy7a92h.aspx