[WINDOWS32] Remove CRNL from FormatMessage() result string

[WINDOWS32] Remove CRNL from FormatMessage() result string

Sometimes the error message is expected to contain a newline, other
times it is not.  Also the result of FormatMessage() sometimes ends
in CRNL already: when printed via fprintf() the final newline is
converted to CRNL, giving an output of CRCRNL which causes tests
to fail to match.  Remove any CR/NL chars from the result string.

* src/job.c (reap_children): Add \n to the error message fprintf.
(exec_command): Ditto.
* src/w32/subproc/w32err.c (map_windows32_error_to_string): Remove
any trailing CR or NL from the string before returning.