fix multi-line ( … ) comments in included files

startup.4th

@@ -1221,6 +1221,10 @@ CREATE EXCEPTION-STACK NULL ,
 
 : PARSE-AREA  ( -- c-addr u )  SOURCE >IN @ /STRING ;
 
+\ Placeholder to be replaced before switching to terminal input
+DEFER REFILL
+' FALSE ' REFILL DEFER!
+
 ' UTILITY (DEFINITIONS)
 
 : PARSE-EMPTY?  ( -- flag )  SOURCE NIP >IN @ = ;
@@ -1235,17 +1239,16 @@ CREATE EXCEPTION-STACK NULL ,
 : SKIP-SPACES  ( "<spaces?>" -- )
    BEGIN ▪ PARSE-EMPTY? 0= WHILE ▪ PEEK-CHAR SPACE? WHILE ▪ SKIP-CHAR ▪ REPEAT ;
 
+: ENSURE-NONEMPTY  ( -- f=eof )
+   BEGIN PARSE-EMPTY? ?0DUP WHILE REFILL 0= ?DUP UNTIL 0= ;
+
 ' FORTH (DEFINITIONS)
 
 \ Comments; ignore all characters until the next EOL or ) character, respectively
 : \  ( "ccc<eol>" -- )  IMMEDIATE
    BEGIN PARSE-EMPTY? 0= WHILE NEXT-CHAR LF = UNTIL ;
 : (  ( "ccc<closeparen>" -- )  IMMEDIATE
-   BEGIN PARSE-EMPTY? 0= WHILE NEXT-CHAR [[ CHAR ) ]] = UNTIL ;
-
-\ Placeholder to be replaced before switching to terminal input
-DEFER REFILL
-' FALSE ' REFILL DEFER!
+   BEGIN ENSURE-NONEMPTY WHILE NEXT-CHAR [[ CHAR ) ]] = UNTIL ;
 
 \ Skip whitespace; read and return the next word delimited by whitespace
 \ The delimiting whitespace character is left in the parse area