Add svrapi.h to the repo as a local include, and make corresponding changes to makefile and readme.

[guy-rouillier]

Add svrapi.h to the repo as a local include, as it has been removed from newer Windows SDKs, and is needed to build TVision. Update the Microsoft make file to add this local include directory if the USE_LOCAL_INCLUDE directive has been specified. The readme.txt is updated to document this new directive.