Extend the text format parser to allow concatenation of string literals in single quotes.

Signed-off-by: David Symonds <dsymonds@golang.org>
diff --git a/proto/text_parser.go b/proto/text_parser.go
index 6d0cf25..4513232 100644
--- a/proto/text_parser.go
+++ b/proto/text_parser.go
@@ -119,6 +119,14 @@
 	return false
 }
 
+func isQuote(c byte) bool {
+	switch c {
+	case '"', '\'':
+		return true
+	}
+	return false
+}
+
 func (p *textParser) skipWhitespace() {
 	i := 0
 	for i < len(p.s) && (isWhitespace(p.s[i]) || p.s[i] == '#') {
@@ -333,13 +341,13 @@
 	p.advance()
 	if p.done {
 		p.cur.value = ""
-	} else if len(p.cur.value) > 0 && p.cur.value[0] == '"' {
+	} else if len(p.cur.value) > 0 && isQuote(p.cur.value[0]) {
 		// Look for multiple quoted strings separated by whitespace,
 		// and concatenate them.
 		cat := p.cur
 		for {
 			p.skipWhitespace()
-			if p.done || p.s[0] != '"' {
+			if p.done || !isQuote(p.s[0]) {
 				break
 			}
 			p.advance()