MXS-1450 Add more string trimming functions

- trim_leading
- trim_trailing

Implemented trim in terms of trim_leading and trim_trailing

include/maxscale/utils.h

@@ -81,7 +81,41 @@ void gw_sha1_2_str(const uint8_t *in, int in_len, const uint8_t *in2, int in2_le
 int gw_getsockerrno(int fd);
 char *create_hex_sha1_sha1_passwd(char *passwd);
 
+/**
+ * Trim leading whitespace from a string.
+ *
+ * @param str String to trim.
+ * @return @c str
+ *
+ * @note If there is leading whitespace, the string is moved so that
+ *       the returned pointer is always the same as the one given as
+ *       argument.
+ */
+char* trim_leading(char* str);
+
+/**
+ * Trim trailing whitespace from a string.
+ *
+ * @param str String to trim.
+ * @return @c str
+ *
+ * @note The returned pointer is always the same the one given as
+ *       argument.
+ */
+char* trim_trailing(char* str);
+
+/**
+ * Trim leading and trailing whitespace from a string.
+ *
+ * @param str String to trim.
+ * @return @c str
+ *
+ * @note If there is leading whitespace, the string is moved so that
+ *       the returned pointer is always the same the one given as
+ *       argument.
+ */
 char* trim(char *str);
+
 char* squeeze_whitespace(char* str);
 bool strip_escape_chars(char*);