hgweb: create Graph methods using a prototype This way it's possible to call the original methods even if they were overridden.

hgweb: remove unused Graph.cur property It was introduced in 0dba955c2636, but was already unused. I missed it in e46f0b653002.

tests: remove shell function helper from test-largefiles-misc Now that all the complexity is in a Python script, we can just directly invoke the tool. Differential Revision: https://phab.mercurial-scm.org/D1599