fix eval qw(BEGIN{die}) style leaks (second attempt).

fix eval qw(BEGIN{die}) style leaks (second attempt).

Repeat of change #28319 (backed out by change #28720), this time
freeing ops using the right pad. Also backs out the remempad
parser addition from change #29501; instead a new auxiliary
paser stack is added, which records the current value of
PL_comppad for every state.
p4raw-link: @29501 on //depot/perl: 2af555bf3f2b3ca8e114df3f5f680d40bd24d6bf
p4raw-link: @28720 on //depot/perl: c86b7e916b443ee192c5638ad9d077ad4e244713
p4raw-link: @28319 on //depot/perl: eb7d7d25d2f780edcbedc124a5bdca0d53ad8687

p4raw-id: //depot/perl@29504