sshpeer: add a configurable hint for the ssh error message
Adding a possibility to configure error hint to be shown in the case of problems with SSH. Example of such hint can be "Please see http://company/internalwiki/ssh.html".
Test Plan:
- Ran hg pull with broken link and verified the output has no hint by default:
```
pulling from ssh://brokenrepository.com//repo
remote: ssh: Could not resolve hostname brokenrepository.com: Name or service not known
abort: no suitable response from remote hg!
```
- Run hg pull --config ui.ssherrorhint="Please see http://company/internalwiki/ssh.html":
```
pulling from ssh://brokenrepository.com//repo
remote: ssh: Could not resolve hostname brokenrepository.com: Name or service not known
abort: no suitable response from remote hg!
(Please see http://company/internalwiki/ssh.html)
```
Differential Revision: https://phab.mercurial-scm.org/D1431
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true