lib: add u16_strcpy/strdup functions

Add u16_strcpy() and u16_strdup(). The latter function will be
used later in implementing efi HII database protocol.

Signed-off-by: Akashi Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>

include/charset.h

@@ -191,6 +191,29 @@ size_t u16_strlen(const u16 *in);
  */
 size_t u16_strnlen(const u16 *in, size_t count);
 
+/**
+ * u16_strcpy() - copy u16 string
+ *
+ * Copy u16 string pointed to by src, including terminating null word, to
+ * the buffer pointed to by dest.
+ *
+ * @dest:		destination buffer
+ * @src:		source buffer (null terminated)
+ * Return:		'dest' address
+ */
+u16 *u16_strcpy(u16 *dest, const u16 *src);
+
+/**
+ * u16_strdup() - duplicate u16 string
+ *
+ * Copy u16 string pointed to by src, including terminating null word, to a
+ * newly allocated buffer.
+ *
+ * @src:		source buffer (null terminated)
+ * Return:		allocated new buffer on success, NULL on failure
+ */
+u16 *u16_strdup(const u16 *src);
+
 /**
  * utf16_to_utf8() - Convert an utf16 string to utf8
  *