mime: base64 encoder: use \n as the line delimiter

ftn2rfc generates normal unix text file for rnews, which then
makes end of lines according to the RFC (\r\n). So, using RFC
ones at the header encoding stage was wrong.

Signed-off-by: Yauheni Kaliuta <y.kaliuta@gmail.com>

src/common/mime.c

@@ -141,7 +141,7 @@ char *mime_dequote(char *d, size_t n, char *s, int flags)
 #define MIME_HEADER_CODE_MIDDLE_QP	"?Q?"
 #define MIME_HEADER_CODE_MIDDLE_B64	"?B?"
 #define MIME_HEADER_CODE_END	"?="
-#define MIME_HEADER_STR_DELIM	"\r\n "
+#define MIME_HEADER_STR_DELIM	"\n "
 #define MIME_STRING_LIMIT 74
 #define MIME_ENC_STRING_LIMIT 80
 #define MIME_MAX_ENC_LEN 31