i18n: add/relocate "i18n keyword" comments for i18n messages in revset.py

revset: use appropriate predicate name in error messages "extinct" and "unstable" predicates use "obsolete" implementation internally, but own predicate name should be used in error messages of them instead of "obsolete".

test-histedit-fold: fix for Windows Fixes 336121088ef1 failing with MSYS. MSYS sh.exe mangled that path by applying its path magic, which caused the test to fail on Windows.

tags: visit new heads in forward order when rebuilding cache This improves performance of building the tag cache by 4x on a repo with ~2800 heads.

identity: show trailing '+' for dirty subrepos (issue2839)

discovery: fix invalid comment about extinct being ignored

obsolete: fix decoding error message arguments

push: do not try to push remote obsolete if local has none

help: fix some instances of 'the the'

pager: work around bug in python 2.4's subprocess module (issue3533) hg v2.2.2 fixed the pager on Windows, but broke it on Python 2.4. This patch only uses the new behavior if Python >= 2.5 is detected.