hg: introduce "wirepeersetupfuncs" to setup wire peer by extensions (issue4109) Since changeset 6f72e7d28b35, "reposetup()" of each extensions is invoked only on repositories enabling corresponded extensions. This causes that largefiles specific interactions between the repository enabling largefiles locally and remote (wire) peer fail, because there is no way to know whether largefiles is enabled on the remote repository behind the wire peer, and largefiles specific "wireproto functions" are not given to any wire peers. To avoid this problem, largefiles should be enabled in wider scope than each repositories (e.g. user-wide "${HOME}/.hgrc"). This patch introduces "wirepeersetupfuncs" to setup wire peer by extensions already enabled. Functions registered into "wirepeersetupfuncs" are invoked for all wire peers. This patch uses plain list instead of "util.hooks" for "wirepeersetupfuncs", because the former allows to control order of function invocation by order of extension enabling: it may be useful for workaround of problems with combination of enabled extensions