Use ddsrt_strsep instead of ddsrt_strtok_r

The two do essentially the same think, and ddsrt_strtok_r was only used
in one place.  (Triggered by Solaris 2.6 not providing strtok_r.)

Signed-off-by: Erik Boasson <eb@ilities.com>

src/ddsrt/include/dds/ddsrt/string.h

@@ -52,21 +52,6 @@ ddsrt_strncasecmp(
   size_t n)
 ddsrt_nonnull((1,2));
 
-/**
- * @brief Split string into tokens.
- *
- * @param[in]     str      String to split into tokens.
- * @param[in]     delim    Characters that delimit a token.
- * @param[in,out] saveptr  Pointer to a char * used internally.
- *
- * @returns The next token or NULL if there are no more tokens.
- */
-DDS_EXPORT char *
-ddsrt_strtok_r(
-  char *str,
-  const char *delim,
-  char **saveptr);
-
 /**
  * @brief Extract token from string.
  *