pathauditor: check for Windows shortname aliases

pathauditor: check for codepoints ignored on OS X

darwin: omit ignorable codepoints when normcase()ing a file path This lets us avoid some nasty case collision problems in OS X with invisible codepoints.

encoding: add hfsignoreclean to clean out HFS-ignored characters According to Apple Technote 1150 (unavailable from Apple as far as I can tell, but archived in several places online), HFS+ ignores sixteen specific unicode runes when doing path normalization. We need to handle those cases, so this function lets us efficiently strip the offending characters from a UTF-8 encoded string (which is the only way it seems to matter on OS X.)

test-casefolding.t: demonstrate a bug with HFS+ ignoring some codepoints

manifest: disallow setting the node id of an entry to None manifest.diff() uses None as a special value to denote the absence of a file, so setting a file node to None means you then can't trust manifest.diff(). This should also make future manifest work slightly easier.

context: stop setting None for modified or added nodes Instead use a magic value, so that we can identify modified or added nodes correctly when using manifest.diff(). Thanks to Martin von Zweigbergk for catching that we have to update _buildstatus as well. That part eluded my debugging for some time.

largefiles: don't actually remove largefiles in an addremove dry run The addlargefiles() method already properly handled dry runs.

bundle2: lowercase part types Since the capitalization no longer carries any meaning (previous diff), this patch normalizes all of the bundle2 part type strings to lower case.

bundle2.bundlepart: make mandatory part flag explicit in API This makes all bundle2 parts mandatory unless they are expressly made advisory via the keyword parameter or the bundlepart.mandatory property.