largefiles: use ui.configpath() where appropriate

largefiles: drop more unnecessary compatibility checks

windows: sanity-check symlink placeholders On Windows, we store symlinks as plain files with the link contents. Via user error or NFS/Samba assistance, these files often end up with 'normal' file contents. Committing these changes thus gives an invalid symlink that can't be checked out on Unix. Here we filter out any modified symlink placeholders that look suspicious when computing status: - more than 1K (looks more like a normal file) - contain NULs (not allowed on Unix, probably a binary) - contains \n (filenames can't contain \n, very unusual for symlinks, very common for files)

largefiles: use util.sha1() instead of hashlib.sha1() everywhere

tests: check for svn >= 1.3 and >= 1.5 in tests that require those versions

convert: add missing import of util, needed for svn < 1.6

run-tests: make sure no_proxy/NO_PROXY are empty to fix test-http-proxy.t If no_proxy (or NO_PROXY) includes localhost, the test for detecting an unreachable proxy fails, because the proxy setting is ignored.