[clang-tidy] use bool literals (#881)

Found with modernize-use-bool-literals

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/scanner.cpp

@@ -51,7 +51,7 @@ Token& Scanner::peek() {
 Mark Scanner::mark() const { return INPUT.mark(); }
 
 void Scanner::EnsureTokensInQueue() {
-  while (1) {
+  while (true) {
     if (!m_tokens.empty()) {
       Token& token = m_tokens.front();
 
@@ -174,7 +174,7 @@ void Scanner::ScanNextToken() {
 }
 
 void Scanner::ScanToNextToken() {
-  while (1) {
+  while (true) {
     // first eat whitespace
     while (INPUT && IsWhitespaceToBeEaten(INPUT.peek())) {
       if (InBlockContext() && Exp::Tab().Matches(INPUT)) {