go/scanner: skip first character if it's a BOM

R=r
CC=golang-dev
https://golang.org/cl/6490095

src/pkg/go/scanner/scanner.go

@@ -125,6 +125,9 @@ func (s *Scanner) Init(file *token.File, src []byte, err ErrorHandler, mode Mode
 	s.ErrorCount = 0
 
 	s.next()
+	if s.ch == '\uFEFF' {
+		s.next() // ignore BOM
+	}
 }
 
 func (s *Scanner) error(offs int, msg string) {
@@ -390,7 +393,7 @@ func (s *Scanner) scanEscape(quote rune) {
 	for ; i > 0 && s.ch != quote && s.ch >= 0; i-- {
 		s.next()
 	}
-	if x > max || 0xd800 <= x && x < 0xe000 {
+	if x > max || 0xD800 <= x && x < 0xE000 {
 		s.error(offs, "escape sequence is invalid Unicode code point")
 	}
 }