parsers: fix a memleak, and add a clearcaches method to the index This change also fixes a nasty memory leak: previously, self->caches was not being freed. The new clearcaches method lets us benchmark with finer granularity, as it lets us separate the cost of loading a revlog index from those of populating and accessing the cache data structures.

hghave: remove symlink test made useless by ac0da5caebec

tests: disable progress estimate in test-debugbuilddag.t If the command takes long enough, including 'estimate' in the format will add some more data to the progress bar output, and make the test fail. See e.g. https://buildd.debian.org/status/fetch.php?pkg=mercurial&arch=kfreebsd-amd64&ver=2.1.2-2&stamp=1333493711