read: Support for MSVC 9.

read: Support for MSVC 9.

* lib/unistd.in.h (read): Replace also when GNULIB_UNISTD_H_NONBLOCKING
is not 1.
* lib/read.c (read_nothrow): New function.
(rpl_read): Define also when GNULIB_NONBLOCKING is not 1. Use
read_nothrow.
* m4/read.m4 (gl_FUNC_READ): Replace read if the platform has an
invalid parameter handler.
(gl_PREREQ_READ): New macro.
* modules/read (Depends-on): Add msvc-inval.
(configure.ac): Invoke gl_PREREQ_READ.
* doc/posix-functions/read.texi: Mention the problem on MSVC.