Fix incorrect comment.

PQmblen and PQdsplen return information about characters, not words.

Kyotaro Horiguchi

src/interfaces/libpq/fe-misc.c

@@ -1180,7 +1180,7 @@ pqSocketPoll(int sock, int forRead, int forWrite, time_t end_time)
  */
 
 /*
- * returns the byte length of the word beginning s, using the
+ * returns the byte length of the character beginning at s, using the
  * specified encoding.
  */
 int
@@ -1190,7 +1190,7 @@ PQmblen(const char *s, int encoding)
 }
 
 /*
- * returns the display length of the word beginning s, using the
+ * returns the display length of the character beginning at s, using the
  * specified encoding.
  */
 int