Remove unreachable duplicate (?#...) parsing code from S_reg()

Remove unreachable duplicate (?#...) parsing code from S_reg()

I believe that this code was rendered unreachable when perl 5.001 added
code to S_nextchar() to skip over embedded comments. Adrian Enache noted
this in March 2003, and proposed a patch which removed it. See
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2003-03/msg00840.html

The patch wasn't applied at that time, and when he sent it again August,
he omitted that hunk. See
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2003-08/msg01820.html

That version was applied as commit e994fd663a4d8acc.