Repository.xs: make remotes() return a list like branches() and refs()
use sv_yes and sv_no instead of creating a new SV
Repository.pm: make tags() return a list like branches(), refs(), etc
xs: update libgit2
Revert "use sv_yes and sv_no instead of creating a new SV"

This reverts commit be6b2de57d68341cd9e32676b8f7925967fe6971.