language/internal: expose StringToBuf

Change-Id: I9c4f59999dcba5ba82839c3a4808d105dd1b88a2
Reviewed-on: https://go-review.googlesource.com/95825
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
Reviewed-by: Nigel Tao <nigeltao@golang.org>

language/internal/language.go

diff --git a/language/internal/language.go b/language/internal/language.go
index 3a6ac06..a036dc7 100644
--- a/language/internal/language.go
+++ b/language/internal/language.go
@@ -125,7 +125,7 @@
 // to the given buffer and returns the number of bytes written. It will never
 // write more than maxCoreSize bytes.
 func (t *Tag) genCoreBytes(buf []byte) int {
-	n := t.LangID.stringToBuf(buf[:])
+	n := t.LangID.StringToBuf(buf[:])
 	if t.ScriptID != 0 {
 		n += copy(buf[n:], "-")
 		n += copy(buf[n:], t.ScriptID.String())

language/internal/lookup.go

diff --git a/language/internal/lookup.go b/language/internal/lookup.go
index da8b598..6294b81 100644
--- a/language/internal/lookup.go
+++ b/language/internal/lookup.go
@@ -128,9 +128,9 @@
 	return 0, ErrSyntax
 }
 
-// stringToBuf writes the string to b and returns the number of bytes
+// StringToBuf writes the string to b and returns the number of bytes
 // written.  cap(b) must be >= 3.
-func (id Language) stringToBuf(b []byte) int {
+func (id Language) StringToBuf(b []byte) int {
 	if id >= langNoIndexOffset {
 		intToStr(uint(id)-langNoIndexOffset, b[:3])
 		return 3