Add a second customizable variable to specify prover args
Add a second customizable variable to specify prover args

This makes it easy to combine user-selected flags with those required by a
project (typically includes, and --lax/--MLish for the compiler).

Suggested-By: da39a3ee5e6b4b0d3255bfef95601890afd80709@aseemr

FStarLang/fstar-mode.el,FStarLang/fstar-mode.el,FStarLang/fstar-mode.el