filelog: allow censored files to contain padding data

To ensure delta compatibility, when a revision is censored, it is
padded to match the original data in size. The previous check does
not allow for padding because it was added before padding was found
to be a requirement.

For more background and design of the censorship feature, see:
mercurial.selenic.com/wiki/CensorPlan

mercurial/filelog.py

@@ -29,7 +29,7 b' def packmeta(meta, text):'
 
 def _censoredtext(text):
     m, offs = parsemeta(text)
-    return m and "censored" in m and not text[offs:]
+    return m and "censored" in m
 
 class filelog(revlog.revlog):
     def __init__(self, opener, path):