Add C style block comments

src/com/craftinginterpreters/lox/Scanner.java

@@ -81,7 +81,14 @@ class Scanner {
                 addToken(SEMICOLON);
                 break;
             case '*':
-                addToken(STAR);
+                if (match('/') && !isAtEnd()) {
+                    advance();
+                } else if (isAtEnd()) {
+                    break;
+                }
+                else {
+                    addToken(STAR);
+                }
                 break;
             case '!':
                 addToken(match('=') ? BANG_EQUAL : BANG);
@@ -98,7 +105,12 @@ class Scanner {
                 if (match('/')) {
                     while (peek() != '\n' && !isAtEnd())
                         advance();
-                } else {
+                } 
+                else if (match('*')) {
+                    while (peek() != '*') 
+                        advance();
+                }
+                else {
                     addToken(SLASH);
                 }
                 break;