[perl #123763] pushre needs to permit OPpTARGET_MY

[perl #123763] pushre needs to permit OPpTARGET_MY

This case fails an assertion:

my($_);0=split

because a pushre op is not expected to have that flag.  A pushre op
starts out as a match op (which may indeed have the flag set), as is
subsequently converted to a pushre op.

[The commit message was written by the committer.]