build,gcrypt.h: Remove INSERT_SYS_SELECT_H.

* configure.ac (INSERT_SYS_SELECT_H): Remove.
Remove checking sys/select.h.
* src/gcrypt.h.in: Remove INSERT_SYS_SELECT_H.

It has been no use any more.

• GnuPG-bug-id: T5637
• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>