A few semantic tweaks for auto-deps.
A few semantic tweaks for auto-deps.

The precedence is determined by the order of the --include
arguments passed on the command-line. If at least an
interface exists, we generate a dependency on the interface
with the highest precedence. If no interface exists, we
generate a dependency on the implementation with the highest
precedence.

A-Manning/FStar,hoheinzollern/FStar,MallabaevAzamat/FStar,hoheinzollern/FStar,FStarLang/FStar,YaccConstructor/FStar,hoheinzollern/FStar,YaccConstructor/FStar,A-Manning/FStar,MallabaevAzamat/FStar,YaccConstructor/FStar,FStarLang/FStar,A-Manning/FStar,MallabaevAzamat/FStar,FStarLang/FStar,MallabaevAzamat/FStar,YaccConstructor/FStar,hoheinzollern/FStar