Fix misleading "Too many open files in system" error message.

The Win32 API GetLastEror() error code 23 is defined in WinError.h as ERROR_CRC "Data error (cyclic redundancy check)" but w32stape.c was incorrectly leaving the CRT 'errno' variable set to that value (23), thereby causing the error message associated with the ENFILE error to be mistakenly issued instead. This should hopefully fix that.