add micromap and list clear

spl/std.spl

@@ -309,6 +309,7 @@ construct List {
     to-stack { .. | :array:to-stack }
     to-str { str | :array:to-str }
     sub { [any] | :array:sub }
+    clear { | :=array<0 anew> }
 }
 construct _GrowingArray {
     ;
@@ -423,6 +424,9 @@ construct MicroMap {
     foreach { | with callable this ;
         callable this:pairs:foreach
     }
+    clear { | with this ;
+        this:pairs:clear;
+    }
 }
 
 construct Range {