Be simpler and more consistent about reporting I/O errors.

Be simpler and more consistent about reporting I/O errors.

* fileio.c (Fcopy_file, Finsert_file_contents, Fwrite_region):
Say "Read error" and "Write error", rather than "I/O error", or
"IO error reading", or "IO error writing", when a read or write
error occurs.
* process.c (Fmake_network_process, wait_reading_process_output)
(send_process, Fprocess_send_eof, wait_reading_process_output):
Capitalize diagnostics consistently.  Put "failed foo" at the
start of the diagnostic, so that we don't capitalize the
function name "foo".  Consistently say "failed" for such
diagnostics.
* sysdep.c, w32.c (serial_open): Now accepts Lisp string, not C string.
All callers changed.  This is so it can use report_file_error.
* sysdep.c (serial_open, serial_configure): Capitalize I/O
diagnostics consistently as above.