changed syntax for file, md5, once, and always from ?thunk into ?action0 ...

SYNTAX

@@ -11,7 +11,7 @@ MAKEFILE:
 <rule-clause> ::= '(' + <rule-clause-identifier>
 		      + <target-spec> 
 	              + <prereq-spec> 
-		      + <action-spec> + ')'
+		      + <action>+ + ')'
 
 <md5-clause> ::= '(' + <md5-clause-identifier>
                      + <target-spec> 
@@ -52,8 +52,6 @@ MAKEFILE:
 <prereq> ::= <filename>
 <prereq-list> ::= '(' + <filename>* + ')'
 
-<action-spec> ::= <action> | <action-list>
-<action> ::= '(' + <thunk>* + ')'
-<action-list> ::= '(' + <action>+ + ')'
+<action> ::= <function-call> | <value>
 
 <filename> ::= '"' + {<dir-separator> + { 'a'-'z''A'-'Z''0'-'9' ... }+ }+ + '"'