feat: complete memory representation gate

source/lexer/scan.hon

@@ -21,6 +21,8 @@ SourceError :: enum { source_too_large }
 @hide:file
 keywords strmap.StaticStringMap(TokenKind) :: strmap.init([
     { "proc", .proc },
+    { "c_func", .c_func },
+    { "null", .null },
     { "return", .return },
     { "break", .break },
     { "continue", .continue },
@@ -297,6 +299,8 @@ scan proc(
             '@': .at
             '&': .ampersand
             '^': .caret
+            '?': .question
+            ';': .semicolon
             '(': .open_paren
             ')': .close_paren
             '[': .open_bracket