Output a string and newline if and only if verbose flag is set.
DESCRIPTION
If the verbose flag is set to true, then the call remark s prints the
string s and a following newline. If the verbose flag is set to false,
this call does nothing. This function is used for informative output in several
automated rules such as MESON.
FAILURE CONDITIONS
Never fails.
EXAMPLE
# remark "Proof is going OK so far";;
Proof is going OK so far
val it : unit = ()
# verbose := false;;
val it : unit = ()
# remark "Proof is going OK so far";;
val it : unit = ()