Fix make doc: escape uses of { and }

Author: alastairreid

libISA/tcheck.ml

@@ -2731,7 +2731,7 @@ let tc_print (env : Env.t) (loc : Loc.t) (args : AST.expr list) : AST.stmt list
       raise (error "Print must always be used with a literal format string like \"x = {x}\"")
   )
 
-(** Extract variable names from a format string like "x={x} y={y}".
+(** Extract variable names from a format string like "x=\{x\} y=\{y\}".
   * Backslash escapes are skipped.
   *)
 let extract_fmt_vars (loc : Loc.t) (fmt : string) : string list =

libISA/utils.mli

@@ -158,10 +158,10 @@ val round_up_to_pow2 : int -> int
 (** Segments of parsed ASL format string *)
 type fmt_segment =
   | Fmt_lit of string  (** Literal text *)
-  | Fmt_var of string  (** Variable from { } *)
+  | Fmt_var of string  (** Variable from \{ \} *)
 
 (** Parse an ASL format string into segments.
-    Raises Failure if { has no matching }. *)
+    Raises Failure if \{ has no matching \}. *)
 val parse_fmt_string : string -> fmt_segment list
 
 (****************************************************************