json: handle capital floating point exponent (1E100).

When parsing numbers with an exponent (like "12e-1"), the JSON scanner
would only allow a lowercase 'e', while the RFC also allows the
uppercase 'E'.

R=adg
CC=golang-dev, rsc
https://golang.org/cl/3986042

src/pkg/json/scanner.go

@@ -416,7 +416,7 @@ func state0(s *scanner, c int) int {
 		s.step = stateDot
 		return scanContinue
 	}
-	if c == 'e' {
+	if c == 'e' || c == 'E' {
 		s.step = stateE
 		return scanContinue
 	}
@@ -440,7 +440,7 @@ func stateDot0(s *scanner, c int) int {
 		s.step = stateDot0
 		return scanContinue
 	}
-	if c == 'e' {
+	if c == 'e' || c == 'E' {
 		s.step = stateE
 		return scanContinue
 	}