set $MANPATH in Bundler::Runtime#setup_environment

This lets `bundle exec man ...` show man pages from bundled gems.
Handle error messages caused by missing binary libraries.
Add ENV[DEBUG_RESOLVER_TREE] which outputs the resolver tree when bundle install.
handle 413 gracefully in verbose mode
Version 1.2.4 and changelog
Stop socket from doing a reverse dns lookup

Conflicts:
	lib/bundler/fetcher.rb
squelch all output during local check resolve
warn on deprecated symbol source
set the right ENV while checking for sudo install
only create bindir once
don't need to path up a path
limit 1.8 tests to 1.8
update 1.2.4 changelog

[ci skip]
backport CertificateFailureError message fix

fixes #2318
oops, error message changed
work even without OpenSSL, but only for http

Conflicts:
	lib/bundler/fetcher.rb
	lib/bundler/vendored_persistent.rb
Remove default version on `gem` method calls since it was never being evaluated
stop shelling out to which
leave .bat gem bins too

fixes #1495
ughhhh so dumb