Revert an assert() fix in the light of change #27152

Revert an assert() fix in the light of change #27152

The MinGW problem described here:
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-01/msg00146.html
was fixed by change #26664. This is no longer relevant in the light of
change #27152, so revert it.

(The other problems with VC++ 6 and BCC, fixed by change #26634, have
not gone away, however.)
p4raw-link: @27152 on //depot/perl: b0e6ae5b51a7c163ac7cdb0d18b54bb1819f6c13
p4raw-link: @26664 on //depot/perl: fb9e8e97420770e8f89d9f2196e1b7b0c855e8bb
p4raw-link: @26634 on //depot/perl: 834268b87a8eb670d899a13106c8dfcdfc7c9b66

p4raw-id: //depot/perl@27171