tests: split out manifest case from test-strip-cross.t...
tests: split out manifest case from test-strip-cross.t
The manifest case was added on after the other cases, in
d67cfe0d4714
(test-strip-cross: test handling of linkrev crosses in the manifest,
2008-01-20). I think it's easier to read and modify if it's separated.
Differential Revision:
https://phab.mercurial-scm.org/D6792