write: Support for MSVC 9.

write: Support for MSVC 9.

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