manual: fix doubled-words and typos
* manual/charset.texi (Selecting the Conversion): Likewise.
* manual/errno.texi (Error Messages): Likewise.
* manual/getopt.texi (Getopt Long Options): Likewise.
* manual/memory.texi (Resizing the Data Segment): Likewise.
* manual/message.texi (GUI program problems): Likewise.
* manual/resource.texi (CPU Affinity): Likewise.
* manual/stdio.texi (Streams and Threads): Likewise.
* manual/time.texi (High Accuracy Clock): Likewise.
(cherry picked from commit
bbf70ae9ce646540576f2b0cbc66b90da1511b0b)