Reorganize the compiler to be bottom-up.

Gets rid of a bunch of forward declarations and shortens the code.
Also makes points of recursion more explicit.

metrics

@@ -11,11 +11,13 @@ num_docs = 0
 num_code = 0
 num_empty = 0
 num_todos = 0
+num_semicolons = 0
 
 for source_path in glob.iglob("src/*.[ch]"):
   num_files += 1
   with open(source_path, "r") as input:
     for line in input:
+      num_semicolons += line.count(';')
       match = TODO_PATTERN.match(line)
       if match:
         num_todos += 1
@@ -37,3 +39,4 @@ print num_todos, "TODOs"
 print num_docs, "comment lines"
 print num_code, "code lines"
 print num_empty, "empty lines"
+print num_semicolons, "semicolons"

test/bool_equality.wren

@@ -0,0 +1,23 @@
+io.write(true == true)    // expect: true
+io.write(true == false)   // expect: false
+io.write(false == true)   // expect: false
+io.write(false == false)  // expect: true
+
+// Not equal to other types.
+io.write(true == 1)        // expect: false
+io.write(false == 0)       // expect: false
+io.write(true == "true")   // expect: false
+io.write(false == "false") // expect: false
+io.write(false == "")      // expect: false
+
+io.write(true != true)    // expect: false
+io.write(true != false)   // expect: true
+io.write(false != true)   // expect: true
+io.write(false != false)  // expect: false
+
+// Not equal to other types.
+io.write(true != 1)        // expect: true
+io.write(false != 0)       // expect: true
+io.write(true != "true")   // expect: true
+io.write(false != "false") // expect: true
+io.write(false != "")      // expect: true