Don't allow "0_0"

Leading zeros wouldn't be detected as the second character isn't a
digit. Make this check more specific to test for 'b', 'o', and 'x'
specifically.

Fixes #326

parse.go

@@ -425,7 +425,7 @@ func (p *parser) valueInlineTable(it item, parentIsArray bool) (interface{}, tom
 // numHasLeadingZero checks if this number has leading zeroes, allowing for '0',
 // +/- signs, and base prefixes.
 func numHasLeadingZero(s string) bool {
-	if len(s) > 1 && s[0] == '0' && isDigit(rune(s[1])) { // >1 to allow "0" and isDigit to allow 0x
+	if len(s) > 1 && s[0] == '0' && !(s[1] == 'b' || s[1] == 'o' || s[1] == 'x') { // Allow 0b, 0o, 0x
 		return true
 	}
 	if len(s) > 2 && (s[0] == '-' || s[0] == '+') && s[1] == '0' {

toml_test.go

@@ -289,7 +289,6 @@ func TestToml(t *testing.T) {
 				"invalid/datetime/time-no-leads",        // https://github.com/BurntSushi/toml/issues/320
 				"invalid/control/bare-null",             // https://github.com/BurntSushi/toml/issues/317
 				"invalid/control/comment-cr",            // https://github.com/BurntSushi/toml/issues/321
-				"invalid/integer/leading-zero-3",        // https://github.com/BurntSushi/toml/issues/326
 				"invalid/string/multiline-bad-escape-3", // https://github.com/BurntSushi/toml/issues/322
 			},
 		}