prebirth: Add `quote' form

* build-aux/bootstrap/prebirth.js (fnmap): Add `quote' form.

build-aux/bootstrap/prebirth.js

@@ -550,6 +550,14 @@ class Compiler
 const fnmap = {
     'js:console': 'console.log',
 
+    // fortunately ES6+ has native symbol support :)
+    // we don't (yet?) need list quoting in Prebirth
+    'quote': ( x, stoes ) => Array.isArray( x.value )
+        ? (function () { throw SyntaxError(
+            "quoting lists is not yet supported; sorry!" )
+        } )()
+        : `Symbol.for('${stoes(x)}')`,
+
     'lambda': ( [ args, ...body ], stoes, btoes ) =>
         "function(" + args.map( stoes ).join( ", " ) + "){\n" +
           btoes( body ) +