Bug #64506 for namespace-alias: ns:a bad peep hooking

namespace-alias-0.01 only passes its tests on 5.8.9 up to 5.10.1. Upon examination, it turns out that this narrow range is largely due to it having a copy of Perl_peep() from the core, which of course changes a lot between Perl versions. However, ns:a actually has no need to copy Perl_peep(): its copy is not modified, nor does ns:a actually need to refer to the base peeper per se. Very much relatedly, ns:a has a serious bug in how it uses the PL_peepp hook: instead of its wrapper (peep_unstrict()) calling the former PL_peepp, it unconditionally calls the copy of the base peeper. Furthermore, the ->setup method overwrites PL_peepp every time it is run, rather than only hooking once. The attached patch fixes both of these issues. It makes ns:a cleanly add itself to the peep hook chain, and drops the now-unneeded copy of the base peeper. This makes ns:a pass its tests from 5.8.8 up to 5.11.1. It still fails on 5.11.2 and above, where there is some other problem that I'll examine shortly. I also tried changing the Perl version requirement declared in alias.pm. It was 5.8.8. Removing this restriction, ns:a passes its test suite all the way down to 5.8.1. I don't see any reason why it wouldn't work on these lower versions in a way that the test suite wouldn't notice. In principle it might work on still lower versions, but B::Hooks::OP::Check requires 5.8.1, so it would require some reworking. The attached patch therefore reduces the declared Perl version requirement to 5.8.1. -zefram