update github.com/pelletier/go-toml to 1.2.0

Rationale: github.com/pelletier/go-toml is the only package that currently
prevents the future vendoring of github.com/golang/dep as it depends on
functions introduced in 1.1.0.

The only consumers of this package are github.com/spf13/viper (used to run e2e
tests) and github.com/bazelbuild/bazel-gazelle (bazel helper), so that's a
pretty low-risk change.

vendor/github.com/pelletier/go-toml/lexer.go

@@ -204,6 +204,14 @@ func (l *tomlLexer) lexRvalue() tomlLexStateFn {
 			return l.lexFalse
 		}
 
+		if l.follow("inf") {
+			return l.lexInf
+		}
+
+		if l.follow("nan") {
+			return l.lexNan
+		}
+
 		if isSpace(next) {
 			l.skip()
 			continue
@@ -265,6 +273,18 @@ func (l *tomlLexer) lexFalse() tomlLexStateFn {
 	return l.lexRvalue
 }
 
+func (l *tomlLexer) lexInf() tomlLexStateFn {
+	l.fastForward(3)
+	l.emit(tokenInf)
+	return l.lexRvalue
+}
+
+func (l *tomlLexer) lexNan() tomlLexStateFn {
+	l.fastForward(3)
+	l.emit(tokenNan)
+	return l.lexRvalue
+}
+
 func (l *tomlLexer) lexEqual() tomlLexStateFn {
 	l.next()
 	l.emit(tokenEqual)
@@ -277,6 +297,8 @@ func (l *tomlLexer) lexComma() tomlLexStateFn {
 	return l.lexRvalue
 }
 
+// Parse the key and emits its value without escape sequences.
+// bare keys, basic string keys and literal string keys are supported.
 func (l *tomlLexer) lexKey() tomlLexStateFn {
 	growingString := ""
 
@@ -287,7 +309,16 @@ func (l *tomlLexer) lexKey() tomlLexStateFn {
 			if err != nil {
 				return l.errorf(err.Error())
 			}
-			growingString += `"` + str + `"`
+			growingString += str
+			l.next()
+			continue
+		} else if r == '\'' {
+			l.next()
+			str, err := l.lexLiteralStringAsString(`'`, false)
+			if err != nil {
+				return l.errorf(err.Error())
+			}
+			growingString += str
 			l.next()
 			continue
 		} else if r == '\n' {
@@ -527,6 +558,7 @@ func (l *tomlLexer) lexTableKey() tomlLexStateFn {
 	return l.lexInsideTableKey
 }
 
+// Parse the key till "]]", but only bare keys are supported
 func (l *tomlLexer) lexInsideTableArrayKey() tomlLexStateFn {
 	for r := l.peek(); r != eof; r = l.peek() {
 		switch r {
@@ -550,6 +582,7 @@ func (l *tomlLexer) lexInsideTableArrayKey() tomlLexStateFn {
 	return l.errorf("unclosed table array key")
 }
 
+// Parse the key till "]" but only bare keys are supported
 func (l *tomlLexer) lexInsideTableKey() tomlLexStateFn {
 	for r := l.peek(); r != eof; r = l.peek() {
 		switch r {
@@ -575,11 +608,77 @@ func (l *tomlLexer) lexRightBracket() tomlLexStateFn {
 	return l.lexRvalue
 }
 
+type validRuneFn func(r rune) bool
+
+func isValidHexRune(r rune) bool {
+	return r >= 'a' && r <= 'f' ||
+		r >= 'A' && r <= 'F' ||
+		r >= '0' && r <= '9' ||
+		r == '_'
+}
+
+func isValidOctalRune(r rune) bool {
+	return r >= '0' && r <= '7' || r == '_'
+}
+
+func isValidBinaryRune(r rune) bool {
+	return r == '0' || r == '1' || r == '_'
+}
+
 func (l *tomlLexer) lexNumber() tomlLexStateFn {
 	r := l.peek()
+
+	if r == '0' {
+		follow := l.peekString(2)
+		if len(follow) == 2 {
+			var isValidRune validRuneFn
+			switch follow[1] {
+			case 'x':
+				isValidRune = isValidHexRune
+			case 'o':
+				isValidRune = isValidOctalRune
+			case 'b':
+				isValidRune = isValidBinaryRune
+			default:
+				if follow[1] >= 'a' && follow[1] <= 'z' || follow[1] >= 'A' && follow[1] <= 'Z' {
+					return l.errorf("unknown number base: %s. possible options are x (hex) o (octal) b (binary)", string(follow[1]))
+				}
+			}
+
+			if isValidRune != nil {
+				l.next()
+				l.next()
+				digitSeen := false
+				for {
+					next := l.peek()
+					if !isValidRune(next) {
+						break
+					}
+					digitSeen = true
+					l.next()
+				}
+
+				if !digitSeen {
+					return l.errorf("number needs at least one digit")
+				}
+
+				l.emit(tokenInteger)
+
+				return l.lexRvalue
+			}
+		}
+	}
+
 	if r == '+' || r == '-' {
 		l.next()
+		if l.follow("inf") {
+			return l.lexInf
+		}
+		if l.follow("nan") {
+			return l.lexNan
+		}
 	}
+
 	pointSeen := false
 	expSeen := false
 	digitSeen := false