subrepo: activate clone pooling to enable sharing with remote URLs This is the easiest way to ensure that repositories with remote subrepo references can share the subrepos, consistent with how local subrepos can be shared.

subrepo: don't attempt to share remote sources (issue5793) Untangling _abssource() to resolve the new subrepo relative to the shared parent's share path, and then either sharing from there (if it exists), or cloning to that location and then sharing, is probably more than should be attempted on stable. Absolute subrepo references are discouraged, so for now, this resumes the behavior prior to 68e0bcb90357 of cloning the absolute subrepo locally.

test-subrepo: demonstrate problems with subrepo sharing and absolute paths This affects remote paths in .hgsub, as well as clone pooling from a remote source. For reasons unknown, there are stability issues with the relative-path.t tests. If run as a single test, it is stable. If run with --loop, or with -jX for X>1, the hash of the parent repo changes. I'm seeing this on both Windows and Fedora 26. I added an `hg log --debug`, and the manifest hash changes, but I have no idea why.

revsetlang: add a hint for more useful parse errors This logic is largely based on the similar logic added to template error messages in D2608 and D2609, but with a few tweaks based on how revsets actually work. Differential Revision: https://phab.mercurial-scm.org/D2619

setup: ignore extension load failures when finding working hg Previously, `make local` would fail if any extension was not properly loading. Differential Revision: https://phab.mercurial-scm.org/D2589

profile: colorize output on Windows Previously, the ANSI codes were printed to the screen, throwing off the alignment. We could probably do this unconditionally, but it's kind of a hack, so I figured I'd limit the scope.