make appendfile simpler so it does not break with revlogng on windows.
it used to cache open files. this made revlogng break because it wants
to rename files when splitting .i into .i/.d, but cannot rename or unlink
open files on windows.
new code is bit slower, but safe on linux and windows. proper fix for
too many open/close of changelog/manifest belongs in different place.
can get 10% speed improvement back.
adding foo
adding bar
adding baz/bletch
test-archive-TIP/bar
test-archive-TIP/baz/bletch
test-archive-TIP/foo
test-archive-TIP/bar
test-archive-TIP/baz/bletch
test-archive-TIP/foo
Archive: archive.zip
testing: test-archive-TIP/bar OK
testing: test-archive-TIP/baz/bletch OK
testing: test-archive-TIP/foo OK
No errors detected in compressed data of archive.zip.