Add CBS_ASN1_UTF8STRING define.

Change-Id: I34384feb46c15c4f443f506d724ad500a4cf0f36
Reviewed-on: https://boringssl-review.googlesource.com/7525
Reviewed-by: David Benjamin <davidben@google.com>

crypto/bytestring/ber.c

@@ -34,6 +34,7 @@ static int is_string_type(unsigned tag) {
   switch (tag & 0x1f) {
     case CBS_ASN1_BITSTRING:
     case CBS_ASN1_OCTETSTRING:
+    case CBS_ASN1_UTF8STRING:
     case CBS_ASN1_NUMERICSTRING:
     case CBS_ASN1_PRINTABLESTRING:
     case CBS_ASN1_T16STRING:

include/openssl/bytestring.h

@@ -128,6 +128,7 @@ OPENSSL_EXPORT int CBS_get_u24_length_prefixed(CBS *cbs, CBS *out);
 #define CBS_ASN1_NULL 0x5
 #define CBS_ASN1_OBJECT 0x6
 #define CBS_ASN1_ENUMERATED 0xa
+#define CBS_ASN1_UTF8STRING 0xc
 #define CBS_ASN1_SEQUENCE (0x10 | CBS_ASN1_CONSTRUCTED)
 #define CBS_ASN1_SET (0x11 | CBS_ASN1_CONSTRUCTED)
 #define CBS_ASN1_NUMERICSTRING 0x12